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1 /* |
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2 * Copyright (c) 2016, 2019, Oracle and/or its affiliates. All rights reserved. |
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
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4 * |
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5 * This code is free software; you can redistribute it and/or modify it |
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6 * under the terms of the GNU General Public License version 2 only, as |
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7 * published by the Free Software Foundation. Oracle designates this |
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8 * particular file as subject to the "Classpath" exception as provided |
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9 * by Oracle in the LICENSE file that accompanied this code. |
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10 * |
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11 * This code is distributed in the hope that it will be useful, but WITHOUT |
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12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or |
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13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License |
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14 * version 2 for more details (a copy is included in the LICENSE file that |
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15 * accompanied this code). |
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16 * |
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17 * You should have received a copy of the GNU General Public License version |
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18 * 2 along with this work; if not, write to the Free Software Foundation, |
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19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. |
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20 * |
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21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
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22 * or visit www.oracle.com if you need additional information or have any |
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23 * questions. |
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24 */ |
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25 |
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26 package java.util.random; |
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27 |
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28 import java.math.BigInteger; |
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29 import java.util.Objects; |
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30 import java.util.stream.DoubleStream; |
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31 import java.util.stream.IntStream; |
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32 import java.util.stream.LongStream; |
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33 import java.util.stream.Stream; |
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34 |
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35 /** |
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36 * The {@link RandomGenerator} interface is designed to provide a common protocol for objects that |
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37 * generate random or (more typically) pseudorandom sequences of numbers (or Boolean values). |
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38 * Such a sequence may be obtained by either repeatedly invoking a method that returns a single |
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39 * (pseudo)randomly chosen value, or by invoking a method that returns a stream of (pseudo)randomly |
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40 * chosen values. |
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41 * <p> |
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42 * Ideally, given an implicitly or explicitly specified range of values, each value would be chosen |
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43 * independently and uniformly from that range. In practice, one may have to settle for some |
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44 * approximation to independence and uniformity. |
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45 * <p> |
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46 * In the case of {@code int}, {@code long}, and {@link Boolean} values, if there is no explicit |
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47 * specification of range, then the range includes all possible values of the type. In the case of |
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48 * {@code float} and {@code double} values, a value is always chosen from the set of |
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49 * 2<sup><i>w</i></sup> values between 0.0 (inclusive) and 1.0 (exclusive), where <i>w</i> is 23 for |
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50 * {@code float} values and 52 for {@code double} values, such that adjacent values differ by |
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51 * 2<sup>−<i>w</i></sup>; if an explicit range is specified, then the chosen number is |
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52 * computationally scaled and translated so as to appear to have been chosen from that range. |
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53 * <p> |
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54 * Each method that returns a stream produces a stream of values each of which is chosen in the same |
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55 * manner as for a method that returns a single (pseudo)randomly chosen value. For example, if |
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56 * {@code r} implements {@link RandomGenerator}, then the method call {@code r.ints(100)} returns a |
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57 * stream of 100 {@code int} values. These are not necessarily the exact same values that would |
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58 * have been returned if instead {@code r.nextInt()} had been called 100 times; all that is |
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59 * guaranteed is that each value in the stream is chosen in a similar (pseudo)random manner from the |
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60 * same range. |
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61 * <p> |
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62 * Every object that implements the {@link RandomNumberGenerator} interface by using a |
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63 * pseudorandom algorithm is assumed to contain a finite amount of state. Using such an object to |
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64 * generate a pseudorandomly chosen value alters its state by computing a new state as a function |
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65 * of the current state, without reference to any information other than the current state. |
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66 * The number of distinct possible states of such an object is called its <i>period</i>. |
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67 * (Some implementations of the {@link RandomNumberGenerator} interface may be truly random |
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68 * rather than pseudorandom, for example relying on the statistical behavior of a physical |
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69 * object to derive chosen values. Such implementations do not have a fixed period.) |
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70 * <p> |
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71 * As a rule, objects that implement the {@link RandomGenerator} interface need not be thread-safe. |
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72 * It is recommended that multithreaded applications use either {@link ThreadLocalRandom} or |
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73 * (preferably) pseudorandom number generators that implement the {@link SplittableGenerator} or |
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74 * {@link JumpableGenerator} interface. |
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75 * <p> |
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76 * To implement this interface, a class only needs to provide concrete definitions for the methods |
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77 * {@code nextLong()} and {@code period()}. Default implementations are provided for all other |
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78 * methods (but it may be desirable to override some of them, especially {@code nextInt()} if the |
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79 * underlying algorithm is {@code int}-based). Moreover, it may be preferable instead to implement |
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80 * a more specialized interface such as {@link JumpableGenerator} or {@link LeapableGenerator}, |
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81 * or to extend an abstract implementation-support class such as {@link AbstractSplittableGenerator} |
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82 * or {@link AbstractArbitrarilyJumpableGenerator}. |
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83 * <p> |
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84 * Objects that implement {@link RandomGenerator} are typically not cryptographically secure. |
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85 * Consider instead using {@link java.security.SecureRandom} to get a cryptographically secure |
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86 * pseudorandom number generator for use by security-sensitive applications. Note, however, that |
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87 * {@code java.security.SecureRandom} does implement the {@link RandomGenerator} interface, so that |
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88 * instances of {@code java.security.SecureRandom} may be used interchangeably with other types of |
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89 * pseudorandom generators in applications that do not require a secure generator. |
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90 * |
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91 * @since 14 |
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92 */ |
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93 public interface RandomGenerator { |
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94 |
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95 /** |
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96 * Supported random number Algorithms. |
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97 */ |
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98 public enum Algorithm { |
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99 /** |
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100 * L64X128MixRandom algorithm |
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101 */ |
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102 L64X128MixRandom("L64X128MixRandom"), |
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103 /** |
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104 * L64X256MixRandom algorithm |
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105 */ |
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106 L64X256MixRandom("L64X256MixRandom"), |
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107 /** |
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108 * L64X1024MixRandom algorithm |
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109 */ |
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110 L64X1024MixRandom("L64X1024MixRandom"), |
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111 /** |
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112 * L128X256MixRandom algorithm |
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113 */ |
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114 L128X256MixRandom("L128X256MixRandom"), |
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115 /** |
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116 * MRG32k3a algorithm |
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117 */ |
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118 MRG32k3a("MRG32k3a"), |
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119 /** |
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120 * Legacy Random algorithm |
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121 */ |
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122 @Deprecated |
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123 Random("Random"), |
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124 /** |
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125 * Legacy SecureRandom algorithm |
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126 */ |
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127 @Deprecated |
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128 SecureRandom("SecureRandom"), |
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129 /** |
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130 * Xoroshiro128StarStar algorithm |
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131 */ |
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132 Xoroshiro128StarStar("Xoroshiro128StarStar"), |
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133 /** |
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134 * Xoshiro256StarStar algorithm |
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135 */ |
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136 Xoshiro256StarStar("Xoshiro256StarStar"); |
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137 |
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138 private String name; |
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139 |
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140 private Algorithm(String name) { |
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141 this.name = name; |
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142 } |
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143 |
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144 public String toString() { |
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145 return name; |
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146 } |
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147 |
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148 /** |
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149 * Returns an instance of {@link RandomGenerator} that utilizes this algorithm. |
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150 * |
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151 * @return An instance of {@link RandomGenerator} |
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152 */ |
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153 public RandomGenerator instance() { |
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154 return RandomGeneratorFactory.of(name, RandomGenerator.class); |
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155 } |
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156 |
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157 /** |
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158 * Returns a {@link RandomGeneratorFactory} that can produce instances |
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159 * of {@link RandomGenerator} that utilizes this algorithm. |
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160 * |
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161 * @return {@link RandomGeneratorFactory} of {@link RandomGenerator} |
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162 */ |
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163 public RandomGeneratorFactory<RandomGenerator> factory() { |
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164 return RandomGeneratorFactory.factoryOf(name, RandomGenerator.class); |
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165 } |
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166 } |
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167 |
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168 /** |
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169 * Returns an instance of {@link RandomGenerator} that utilizes the |
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170 * {@code name} algorithm. |
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171 * |
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172 * @param name Name of random number generator algorithm |
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173 * |
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174 * @return An instance of {@link RandomGenerator} |
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175 */ |
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176 public static RandomGenerator of(String name) { |
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177 Objects.requireNonNull(name); |
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178 return RandomGeneratorFactory.of(name, RandomGenerator.class); |
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179 } |
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180 |
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181 /** |
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182 * Returns an instance of {@link RandomGenerator} that utilizes the |
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183 * specified {@code algorithm}. |
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184 * |
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185 * @param algorithm Random number generator algorithm |
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186 * |
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187 * @return An instance of {@link RandomGenerator} |
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188 */ |
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189 public static RandomGenerator of(Algorithm algorithm) { |
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190 Objects.requireNonNull(algorithm); |
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191 return RandomGeneratorFactory.of(algorithm.toString(), RandomGenerator.class); |
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192 } |
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193 |
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194 /** |
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195 * Returns a {@link RandomGeneratorFactory} that can produce instances |
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196 * of {@link RandomGenerator} that utilizes the {@code name} algorithm. |
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197 * |
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198 * @param name Name of random number generator algorithm |
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199 * |
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200 * @return {@link RandomGeneratorFactory} of {@link RandomGenerator} |
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201 */ |
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202 public static RandomGeneratorFactory<RandomGenerator> factoryOf(String name) { |
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203 Objects.requireNonNull(name); |
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204 return RandomGeneratorFactory.factoryOf(name, RandomGenerator.class); |
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205 } |
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206 |
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207 /** |
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208 * Returns a {@link RandomGeneratorFactory} that can produce instances |
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209 * of {@link RandomGenerator} that utilizes the specified {@code algorithm}. |
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210 * |
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211 * @param algorithm Random number generator algorithm |
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212 * |
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213 * @return {@link RandomGeneratorFactory} of {@link RandomGenerator} |
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214 */ |
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215 public static RandomGeneratorFactory<RandomGenerator> factoryOf(Algorithm algorithm) { |
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216 Objects.requireNonNull(algorithm); |
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217 return RandomGeneratorFactory.factoryOf(algorithm.toString(), RandomGenerator.class); |
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218 } |
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219 |
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220 /** |
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221 * Returns an effectively unlimited stream of pseudorandomly chosen |
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222 * {@code double} values. |
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223 * |
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224 * @return a stream of pseudorandomly chosen {@code double} values |
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225 * |
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226 * @implNote It is permitted to implement this method in a manner |
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227 * equivalent to {@code doubles(Long.MAX_VALUE)}. |
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228 * |
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229 * @implNote The default implementation produces a sequential stream |
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230 * that repeatedly calls {@code nextDouble()}. |
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231 */ |
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232 default DoubleStream doubles() { |
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233 return DoubleStream.generate(this::nextDouble).sequential(); |
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234 } |
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235 |
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236 /** |
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237 * Returns an effectively unlimited stream of pseudorandomly chosen |
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238 * {@code double} values, where each value is between the specified |
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239 * origin (inclusive) and the specified bound (exclusive). |
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240 * |
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241 * @param randomNumberOrigin the least value that can be produced |
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242 * @param randomNumberBound the upper bound (exclusive) for each value produced |
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243 * |
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244 * @return a stream of pseudorandomly chosen {@code double} values, each between |
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245 * the specified origin (inclusive) and the specified bound (exclusive) |
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246 * |
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247 * @throws IllegalArgumentException if {@code randomNumberOrigin} is not finite, |
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248 * or {@code randomNumberBound} is not finite, or {@code randomNumberOrigin} |
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249 * is greater than or equal to {@code randomNumberBound} |
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250 * |
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251 * @implNote It is permitted to implement this method in a manner equivalent to |
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252 * {@code doubles(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}. |
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253 * @implNote The default implementation produces a sequential stream that repeatedly |
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254 * calls {@code nextDouble(randomNumberOrigin, randomNumberBound)}. |
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255 */ |
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256 default DoubleStream doubles(double randomNumberOrigin, double randomNumberBound) { |
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257 RandomSupport.checkRange(randomNumberOrigin, randomNumberBound); |
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258 return DoubleStream.generate(() -> nextDouble(randomNumberOrigin, randomNumberBound)).sequential(); |
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259 } |
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260 |
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261 /** |
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262 * Returns a stream producing the given {@code streamSize} number of |
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263 * pseudorandomly chosen {@code double} values. |
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264 * |
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265 * @param streamSize the number of values to generate |
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266 * |
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267 * @return a stream of pseudorandomly chosen {@code double} values |
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268 * |
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269 * @throws IllegalArgumentException if {@code streamSize} is |
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270 * less than zero |
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271 * |
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272 * @implNote The default implementation produces a sequential stream |
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273 * that repeatedly calls {@code nextDouble()}. |
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274 */ |
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275 default DoubleStream doubles(long streamSize) { |
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276 RandomSupport.checkStreamSize(streamSize); |
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277 return doubles().limit(streamSize); |
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278 } |
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279 |
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280 /** |
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281 * Returns a stream producing the given {@code streamSize} number of |
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282 * pseudorandomly chosen {@code double} values, where each value is between |
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283 * the specified origin (inclusive) and the specified bound (exclusive). |
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284 * |
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285 * @param streamSize the number of values to generate |
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286 * @param randomNumberOrigin the least value that can be produced |
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287 * @param randomNumberBound the upper bound (exclusive) for each value produced |
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288 * |
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289 * @return a stream of pseudorandomly chosen {@code double} values, each between |
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290 * the specified origin (inclusive) and the specified bound (exclusive) |
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291 * |
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292 * @throws IllegalArgumentException if {@code streamSize} is less than zero, |
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293 * or {@code randomNumberOrigin} is not finite, |
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294 * or {@code randomNumberBound} is not finite, or {@code randomNumberOrigin} |
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295 * is greater than or equal to {@code randomNumberBound} |
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296 * |
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297 * @implNote The default implementation produces a sequential stream that repeatedly |
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298 * calls {@code nextDouble(randomNumberOrigin, randomNumberBound)}. |
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299 */ |
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300 default DoubleStream doubles(long streamSize, double randomNumberOrigin, |
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301 double randomNumberBound) { |
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302 RandomSupport.checkStreamSize(streamSize); |
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303 RandomSupport.checkRange(randomNumberOrigin, randomNumberBound); |
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304 return doubles(randomNumberOrigin, randomNumberBound).limit(streamSize); |
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305 } |
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306 |
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307 /** |
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308 * Returns an effectively unlimited stream of pseudorandomly chosen |
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309 * {@code int} values. |
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310 * |
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311 * @return a stream of pseudorandomly chosen {@code int} values |
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312 * |
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313 * @implNote It is permitted to implement this method in a manner |
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314 * equivalent to {@code ints(Long.MAX_VALUE)}. |
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315 * @implNote The default implementation produces a sequential stream |
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316 * that repeatedly calls {@code nextInt()}. |
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317 */ |
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318 default IntStream ints() { |
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319 return IntStream.generate(this::nextInt).sequential(); |
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320 } |
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321 |
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322 /** |
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323 * Returns an effectively unlimited stream of pseudorandomly chosen |
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324 * {@code int} values, where each value is between the specified |
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325 * origin (inclusive) and the specified bound (exclusive). |
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326 * |
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327 * @param randomNumberOrigin the least value that can be produced |
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328 * @param randomNumberBound the upper bound (exclusive) for each value produced |
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329 * |
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330 * @return a stream of pseudorandomly chosen {@code int} values, each between |
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331 * the specified origin (inclusive) and the specified bound (exclusive) |
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332 * |
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333 * @throws IllegalArgumentException if {@code randomNumberOrigin} |
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334 * is greater than or equal to {@code randomNumberBound} |
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335 * |
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336 * @implNote It is permitted to implement this method in a manner equivalent to |
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337 * {@code ints(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}. |
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338 * @implNote The default implementation produces a sequential stream that repeatedly |
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339 * calls {@code nextInt(randomNumberOrigin, randomNumberBound)}. |
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340 */ |
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341 default IntStream ints(int randomNumberOrigin, int randomNumberBound) { |
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342 RandomSupport.checkRange(randomNumberOrigin, randomNumberBound); |
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343 return IntStream.generate(() -> nextInt(randomNumberOrigin, randomNumberBound)).sequential(); |
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344 } |
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345 |
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346 /** |
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347 * Returns a stream producing the given {@code streamSize} number of |
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348 * pseudorandomly chosen {@code int} values. |
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349 * |
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350 * @param streamSize the number of values to generate |
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351 * |
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352 * @return a stream of pseudorandomly chosen {@code int} values |
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353 * |
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354 * @throws IllegalArgumentException if {@code streamSize} is |
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355 * less than zero |
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356 * |
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357 * @implNote The default implementation produces a sequential stream |
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358 * that repeatedly calls {@code nextInt()}. |
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359 */ |
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360 default IntStream ints(long streamSize) { |
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361 RandomSupport.checkStreamSize(streamSize); |
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362 return ints().limit(streamSize); |
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363 } |
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364 |
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365 /** |
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366 * Returns a stream producing the given {@code streamSize} number of |
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367 * pseudorandomly chosen {@code int} values, where each value is between |
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368 * the specified origin (inclusive) and the specified bound (exclusive). |
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369 * |
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370 * @param streamSize the number of values to generate |
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371 * @param randomNumberOrigin the least value that can be produced |
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372 * @param randomNumberBound the upper bound (exclusive) for each value produced |
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373 * |
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374 * @return a stream of pseudorandomly chosen {@code int} values, each between |
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375 * the specified origin (inclusive) and the specified bound (exclusive) |
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376 * |
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377 * @throws IllegalArgumentException if {@code streamSize} is |
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378 * less than zero, or {@code randomNumberOrigin} |
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379 * is greater than or equal to {@code randomNumberBound} |
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380 * |
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381 * @implNote The default implementation produces a sequential stream that repeatedly |
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382 * calls {@code nextInt(randomNumberOrigin, randomNumberBound)}. |
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383 */ |
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384 default IntStream ints(long streamSize, int randomNumberOrigin, |
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385 int randomNumberBound) { |
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386 RandomSupport.checkStreamSize(streamSize); |
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387 RandomSupport.checkRange(randomNumberOrigin, randomNumberBound); |
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388 return ints(randomNumberOrigin, randomNumberBound).limit(streamSize); |
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389 } |
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390 |
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391 /** |
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392 * Returns an effectively unlimited stream of pseudorandomly chosen |
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393 * {@code long} values. |
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394 * |
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395 * @return a stream of pseudorandomly chosen {@code long} values |
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396 * |
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397 * @implNote It is permitted to implement this method in a manner |
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398 * equivalent to {@code longs(Long.MAX_VALUE)}. |
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399 * @implNote The default implementation produces a sequential stream |
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400 * that repeatedly calls {@code nextLong()}. |
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401 */ |
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402 default LongStream longs() { |
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403 return LongStream.generate(this::nextLong).sequential(); |
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404 } |
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405 |
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406 /** |
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407 * Returns an effectively unlimited stream of pseudorandomly chosen |
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408 * {@code long} values, where each value is between the specified |
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409 * origin (inclusive) and the specified bound (exclusive). |
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410 * |
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411 * @param randomNumberOrigin the least value that can be produced |
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412 * @param randomNumberBound the upper bound (exclusive) for each value produced |
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413 * |
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414 * @return a stream of pseudorandomly chosen {@code long} values, each between |
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415 * the specified origin (inclusive) and the specified bound (exclusive) |
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416 * |
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417 * @throws IllegalArgumentException if {@code randomNumberOrigin} |
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418 * is greater than or equal to {@code randomNumberBound} |
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419 * |
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420 * @implNote It is permitted to implement this method in a manner equivalent to |
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421 * {@code longs(Long.MAX_VALUE, randomNumberOrigin, randomNumberBound)}. |
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422 * @implNote The default implementation produces a sequential stream that repeatedly |
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423 * calls {@code nextLong(randomNumberOrigin, randomNumberBound)}. |
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424 */ |
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425 default LongStream longs(long randomNumberOrigin, long randomNumberBound) { |
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426 RandomSupport.checkRange(randomNumberOrigin, randomNumberBound); |
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427 return LongStream.generate(() -> nextLong(randomNumberOrigin, randomNumberBound)).sequential(); |
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428 } |
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429 |
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430 /** |
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431 * Returns a stream producing the given {@code streamSize} number of |
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432 * pseudorandomly chosen {@code long} values. |
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433 * |
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434 * @param streamSize the number of values to generate |
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435 * |
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436 * @return a stream of pseudorandomly chosen {@code long} values |
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437 * |
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438 * @throws IllegalArgumentException if {@code streamSize} is |
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439 * less than zero |
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440 * |
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441 * @implNote The default implementation produces a sequential stream |
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442 * that repeatedly calls {@code nextLong()}. |
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443 */ |
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444 default LongStream longs(long streamSize) { |
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445 RandomSupport.checkStreamSize(streamSize); |
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446 return longs().limit(streamSize); |
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447 } |
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448 |
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449 /** |
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450 * Returns a stream producing the given {@code streamSize} number of |
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451 * pseudorandomly chosen {@code long} values, where each value is between |
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452 * the specified origin (inclusive) and the specified bound (exclusive). |
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453 * |
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454 * @param streamSize the number of values to generate |
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455 * @param randomNumberOrigin the least value that can be produced |
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456 * @param randomNumberBound the upper bound (exclusive) for each value produced |
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457 * |
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458 * @return a stream of pseudorandomly chosen {@code long} values, each between |
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459 * the specified origin (inclusive) and the specified bound (exclusive) |
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460 * |
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461 * @throws IllegalArgumentException if {@code streamSize} is |
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462 * less than zero, or {@code randomNumberOrigin} |
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463 * is greater than or equal to {@code randomNumberBound} |
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464 * |
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465 * @implNote The default implementation produces a sequential stream that repeatedly |
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466 * calls {@code nextLong(randomNumberOrigin, randomNumberBound)}. |
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467 */ |
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468 default LongStream longs(long streamSize, long randomNumberOrigin, |
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469 long randomNumberBound) { |
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470 RandomSupport.checkStreamSize(streamSize); |
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471 RandomSupport.checkRange(randomNumberOrigin, randomNumberBound); |
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472 return longs(randomNumberOrigin, randomNumberBound).limit(streamSize); |
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473 } |
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474 |
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475 /** |
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476 * Returns a pseudorandomly chosen {@code boolean} value. |
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477 * <p> |
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478 * The default implementation tests the high-order bit (sign bit) of a value produced by |
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479 * {@code nextInt()}, on the grounds that some algorithms for pseudorandom number generation |
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480 * produce values whose high-order bits have better statistical quality than the low-order bits. |
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481 * |
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482 * @return a pseudorandomly chosen {@code boolean} value |
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483 */ |
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484 default boolean nextBoolean() { |
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485 return nextInt() < 0; |
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486 } |
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487 |
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488 /** |
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489 * Returns a pseudorandom {@code float} value between zero (inclusive) and one (exclusive). |
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490 * <p> |
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491 * The default implementation uses the 24 high-order bits from a call to {@code nextInt()}. |
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492 * |
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493 * @return a pseudorandom {@code float} value between zero (inclusive) and one (exclusive) |
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494 */ |
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495 default float nextFloat() { |
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496 return (nextInt() >>> 8) * 0x1.0p-24f; |
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497 } |
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498 |
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499 /** |
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500 * Returns a pseudorandomly chosen {@code float} value between zero |
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501 * (inclusive) and the specified bound (exclusive). |
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502 * |
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503 * @param bound the upper bound (exclusive) for the returned value. |
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504 * Must be positive and finite |
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505 * |
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506 * @return a pseudorandomly chosen {@code float} value between |
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507 * zero (inclusive) and the bound (exclusive) |
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508 * |
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509 * @throws IllegalArgumentException if {@code bound} is not |
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510 * both positive and finite |
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511 * |
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512 * @implNote The default implementation simply calls |
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513 * {@code RandomSupport.checkBound(bound)} and then |
|
514 * {@code RandomSupport.boundedNextFloat(this, bound)}. |
|
515 */ |
|
516 default float nextFloat(float bound) { |
|
517 RandomSupport.checkBound(bound); |
|
518 return RandomSupport.boundedNextFloat(this, bound); |
|
519 } |
|
520 |
|
521 /** |
|
522 * Returns a pseudorandomly chosen {@code float} value between the |
|
523 * specified origin (inclusive) and the specified bound (exclusive). |
|
524 * |
|
525 * @param origin the least value that can be returned |
|
526 * @param bound the upper bound (exclusive) |
|
527 * |
|
528 * @return a pseudorandomly chosen {@code float} value between the |
|
529 * origin (inclusive) and the bound (exclusive) |
|
530 * |
|
531 * @throws IllegalArgumentException if {@code origin} is not finite, |
|
532 * or {@code bound} is not finite, or {@code origin} |
|
533 * is greater than or equal to {@code bound} |
|
534 * |
|
535 * @implNote The default implementation simply calls |
|
536 * {@code RandomSupport.checkRange(origin, bound)} and then |
|
537 * {@code RandomSupport.boundedNextFloat(this, origin, bound)}. |
|
538 */ |
|
539 default float nextFloat(float origin, float bound) { |
|
540 RandomSupport.checkRange(origin, bound); |
|
541 return RandomSupport.boundedNextFloat(this, origin, bound); |
|
542 } |
|
543 |
|
544 /** |
|
545 * Returns a pseudorandom {@code double} value between zero (inclusive) and one (exclusive). |
|
546 * <p> |
|
547 * The default implementation uses the 53 high-order bits from a call to {@code nextLong()}. |
|
548 * |
|
549 * @return a pseudorandom {@code double} value between zero (inclusive) and one (exclusive) |
|
550 */ |
|
551 default double nextDouble() { |
|
552 return (nextLong() >>> 11) * 0x1.0p-53; |
|
553 } |
|
554 |
|
555 /** |
|
556 * Returns a pseudorandomly chosen {@code double} value between zero |
|
557 * (inclusive) and the specified bound (exclusive). |
|
558 * |
|
559 * @param bound the upper bound (exclusive) for the returned value. |
|
560 * Must be positive and finite |
|
561 * |
|
562 * @return a pseudorandomly chosen {@code double} value between |
|
563 * zero (inclusive) and the bound (exclusive) |
|
564 * |
|
565 * @throws IllegalArgumentException if {@code bound} is not |
|
566 * both positive and finite |
|
567 * |
|
568 * @implNote The default implementation simply calls |
|
569 * {@code RandomSupport.checkBound(bound)} and then |
|
570 * {@code RandomSupport.boundedNextDouble(this, bound)}. |
|
571 */ |
|
572 default double nextDouble(double bound) { |
|
573 RandomSupport.checkBound(bound); |
|
574 return RandomSupport.boundedNextDouble(this, bound); |
|
575 } |
|
576 |
|
577 /** |
|
578 * Returns a pseudorandomly chosen {@code double} value between the |
|
579 * specified origin (inclusive) and the specified bound (exclusive). |
|
580 * |
|
581 * @param origin the least value that can be returned |
|
582 * @param bound the upper bound (exclusive) for the returned value |
|
583 * |
|
584 * @return a pseudorandomly chosen {@code double} value between the |
|
585 * origin (inclusive) and the bound (exclusive) |
|
586 * |
|
587 * @throws IllegalArgumentException if {@code origin} is not finite, |
|
588 * or {@code bound} is not finite, or {@code origin} |
|
589 * is greater than or equal to {@code bound} |
|
590 * |
|
591 * @implNote The default implementation simply calls |
|
592 * {@code RandomSupport.checkRange(origin, bound)} and then |
|
593 * {@code RandomSupport.boundedNextDouble(this, origin, bound)}. |
|
594 */ |
|
595 default double nextDouble(double origin, double bound) { |
|
596 RandomSupport.checkRange(origin, bound); |
|
597 return RandomSupport.boundedNextDouble(this, origin, bound); |
|
598 } |
|
599 |
|
600 /** |
|
601 * Returns a pseudorandomly chosen {@code int} value. |
|
602 * <p> |
|
603 * The default implementation uses the 32 high-order bits from a call to {@code nextLong()}. |
|
604 * |
|
605 * @return a pseudorandomly chosen {@code int} value |
|
606 */ |
|
607 default public int nextInt() { |
|
608 return (int)(nextLong() >>> 32); |
|
609 } |
|
610 |
|
611 /** |
|
612 * Returns a pseudorandomly chosen {@code int} value between |
|
613 * zero (inclusive) and the specified bound (exclusive). |
|
614 * |
|
615 * @param bound the upper bound (exclusive) for the returned value. Must be positive. |
|
616 * |
|
617 * @return a pseudorandomly chosen {@code int} value between |
|
618 * zero (inclusive) and the bound (exclusive) |
|
619 * |
|
620 * @throws IllegalArgumentException if {@code bound} is not positive |
|
621 * |
|
622 * @implNote The default implementation simply calls |
|
623 * {@code RandomSupport.checkBound(bound)} and then |
|
624 * {@code RandomSupport.boundedNextInt(this, bound)}. |
|
625 */ |
|
626 default int nextInt(int bound) { |
|
627 RandomSupport.checkBound(bound); |
|
628 return RandomSupport.boundedNextInt(this, bound); |
|
629 } |
|
630 |
|
631 /** |
|
632 * Returns a pseudorandomly chosen {@code int} value between the |
|
633 * specified origin (inclusive) and the specified bound (exclusive). |
|
634 * |
|
635 * @param origin the least value that can be returned |
|
636 * @param bound the upper bound (exclusive) for the returned value |
|
637 * |
|
638 * @return a pseudorandomly chosen {@code int} value between the |
|
639 * origin (inclusive) and the bound (exclusive) |
|
640 * |
|
641 * @throws IllegalArgumentException if {@code origin} is greater than |
|
642 * or equal to {@code bound} |
|
643 * |
|
644 * @implNote The default implementation simply calls |
|
645 * {@code RandomSupport.checkRange(origin, bound)} and then |
|
646 * {@code RandomSupport.boundedNextInt(this, origin, bound)}. |
|
647 */ |
|
648 default int nextInt(int origin, int bound) { |
|
649 RandomSupport.checkRange(origin, bound); |
|
650 return RandomSupport.boundedNextInt(this, origin, bound); |
|
651 } |
|
652 |
|
653 /** |
|
654 * Returns a pseudorandomly chosen {@code long} value. |
|
655 * |
|
656 * @return a pseudorandomly chosen {@code long} value |
|
657 */ |
|
658 long nextLong(); |
|
659 |
|
660 /** |
|
661 * Returns a pseudorandomly chosen {@code long} value between |
|
662 * zero (inclusive) and the specified bound (exclusive). |
|
663 * |
|
664 * @param bound the upper bound (exclusive) for the returned value. Must be positive. |
|
665 * |
|
666 * @return a pseudorandomly chosen {@code long} value between |
|
667 * zero (inclusive) and the bound (exclusive) |
|
668 * |
|
669 * @throws IllegalArgumentException if {@code bound} is not positive |
|
670 * |
|
671 * @implNote The default implementation simply calls |
|
672 * {@code RandomSupport.checkBound(bound)} and then |
|
673 * {@code RandomSupport.boundedNextLong(this, bound)}. |
|
674 */ |
|
675 default long nextLong(long bound) { |
|
676 RandomSupport.checkBound(bound); |
|
677 return RandomSupport.boundedNextLong(this, bound); |
|
678 } |
|
679 |
|
680 /** |
|
681 * Returns a pseudorandomly chosen {@code long} value between the |
|
682 * specified origin (inclusive) and the specified bound (exclusive). |
|
683 * |
|
684 * @param origin the least value that can be returned |
|
685 * @param bound the upper bound (exclusive) for the returned value |
|
686 * |
|
687 * @return a pseudorandomly chosen {@code long} value between the |
|
688 * origin (inclusive) and the bound (exclusive) |
|
689 * |
|
690 * @throws IllegalArgumentException if {@code origin} is greater than |
|
691 * or equal to {@code bound} |
|
692 * |
|
693 * @implNote The default implementation simply calls |
|
694 * {@code RandomSupport.checkRange(origin, bound)} and then |
|
695 * {@code RandomSupport.boundedNextInt(this, origin, bound)}. |
|
696 * |
|
697 */ |
|
698 default long nextLong(long origin, long bound) { |
|
699 RandomSupport.checkRange(origin, bound); |
|
700 return RandomSupport.boundedNextLong(this, origin, bound); |
|
701 } |
|
702 |
|
703 /** |
|
704 * Returns a {@code double} value pseudorandomly chosen from |
|
705 * a Gaussian (normal) distribution whose mean is 0 and whose |
|
706 * standard deviation is 1. |
|
707 * |
|
708 * @return a {@code double} value pseudorandomly chosen from a |
|
709 * Gaussian distribution |
|
710 */ |
|
711 default double nextGaussian() { |
|
712 return RandomSupport.computeNextGaussian(this); |
|
713 } |
|
714 |
|
715 /** |
|
716 * Returns a {@code double} value pseudorandomly chosen from |
|
717 * a Gaussian (normal) distribution with a mean and |
|
718 * standard deviation specified by the arguments. |
|
719 * |
|
720 * @param mean the mean of the Gaussian distribution to be drawn from |
|
721 * @param stddev the standard deviation (square root of the variance) |
|
722 * of the Gaussian distribution to be drawn from |
|
723 * |
|
724 * @return a {@code double} value pseudorandomly chosen from the |
|
725 * specified Gaussian distribution |
|
726 * |
|
727 * @throws IllegalArgumentException if {@code stddev} is negative |
|
728 */ |
|
729 default double nextGaussian(double mean, double stddev) { |
|
730 if (stddev < 0.0) throw new IllegalArgumentException("standard deviation must be non-negative"); |
|
731 return mean + stddev * RandomSupport.computeNextGaussian(this); |
|
732 } |
|
733 |
|
734 /** |
|
735 * Returns a nonnegative {@code double} value pseudorandomly chosen |
|
736 * from an exponential distribution whose mean is 1. |
|
737 * |
|
738 * @return a nonnegative {@code double} value pseudorandomly chosen from an |
|
739 * exponential distribution |
|
740 */ |
|
741 default double nextExponential() { |
|
742 return RandomSupport.computeNextExponential(this); |
|
743 } |
|
744 |
|
745 /** |
|
746 * Returns the period of this {@link RandomGenerator} object. |
|
747 * |
|
748 * @return a {@link BigInteger} whose value is the number of distinct possible states of this |
|
749 * {@link RandomGenerator} object, or 0 if unknown, or negative if extremely |
|
750 * large. |
|
751 */ |
|
752 BigInteger period(); |
|
753 |
|
754 /** |
|
755 * The value (0) returned by the {@code period()} method if the period is unknown. |
|
756 */ |
|
757 static final BigInteger UNKNOWN_PERIOD = BigInteger.ZERO; |
|
758 |
|
759 /** |
|
760 * The (negative) value returned by the {@code period()} method if this generator |
|
761 * has no period because it is truly random rather than just pseudorandom. |
|
762 */ |
|
763 static final BigInteger TRULY_RANDOM = BigInteger.valueOf(-1); |
|
764 |
|
765 /** |
|
766 * The (negative) value that may be returned by the {@code period()} method |
|
767 * if this generator has a huge period (larger than 2**(2**16)). |
|
768 */ |
|
769 static final BigInteger HUGE_PERIOD = BigInteger.valueOf(-2); |
|
770 |
|
771 /** |
|
772 * The {@link StreamableGenerator} interface augments the {@link RandomGenerator} interface |
|
773 * to provide methods that return streams of {@link RandomGenerator} objects. |
|
774 * Ideally, such a stream of objects would have the property that the |
|
775 * behavior of each object is statistically independent of all the others. |
|
776 * In practice, one may have to settle for some approximation to this property. |
|
777 * |
|
778 * A generator that implements interface {@link SplittableGenerator} |
|
779 * may choose to use its {@code splits} method to implement the {@code rngs} |
|
780 * method required by this interface. |
|
781 * |
|
782 * A generator that implements interface {@link JumpableGenerator} |
|
783 * may choose to use its {@code jumps} method to implement the {@code rngs} |
|
784 * method required by this interface. |
|
785 * |
|
786 * A generator that implements interface {@link LeapableGenerator} |
|
787 * may choose to use its {@code leaps} method to implement the {@code rngs} |
|
788 * method required by this interface. |
|
789 * <p> |
|
790 * An implementation of the {@link StreamableGenerator} interface must provide |
|
791 * concrete definitions for the methods {@code nextInt()}, {@code nextLong}, |
|
792 * {@code period()}, and {@code rngs()}. |
|
793 * Default implementations are provided for all other methods. |
|
794 * <p> |
|
795 * Objects that implement {@link StreamableGenerator} are typically |
|
796 * not cryptographically secure. Consider instead using |
|
797 * {@link java.security.SecureRandom} to get a cryptographically |
|
798 * secure pseudo-random number generator for use by |
|
799 * security-sensitive applications. |
|
800 * |
|
801 * @since 14 |
|
802 */ |
|
803 public interface StreamableGenerator extends RandomGenerator { |
|
804 |
|
805 /** |
|
806 * Returns an instance of {@link StreamableGenerator} that utilizes the |
|
807 * {@code name} algorithm. |
|
808 * |
|
809 * @param name Name of random number generator algorithm |
|
810 * |
|
811 * @return An instance of {@link StreamableGenerator} |
|
812 */ |
|
813 public static StreamableGenerator of(String name) { |
|
814 Objects.requireNonNull(name); |
|
815 return RandomGeneratorFactory.of(name, StreamableGenerator.class); |
|
816 } |
|
817 |
|
818 /** |
|
819 * Returns an instance of {@link StreamableGenerator} that utilizes the |
|
820 * specified {@code algorithm}. |
|
821 * |
|
822 * @param algorithm Random number generator algorithm |
|
823 * |
|
824 * @return An instance of {@link StreamableGenerator} |
|
825 */ |
|
826 public static StreamableGenerator of(Algorithm algorithm) { |
|
827 Objects.requireNonNull(algorithm); |
|
828 return RandomGeneratorFactory.of(algorithm.toString(), StreamableGenerator.class); |
|
829 } |
|
830 |
|
831 /** |
|
832 * Returns a {@link RandomGeneratorFactory} that can produce instances |
|
833 * of {@link StreamableGenerator} that utilizes the {@code name} algorithm. |
|
834 * |
|
835 * @param name Name of random number generator algorithm |
|
836 * |
|
837 * @return {@link RandomGeneratorFactory} of {@link StreamableGenerator} |
|
838 */ |
|
839 public static RandomGeneratorFactory<StreamableGenerator> factoryOf(String name) { |
|
840 Objects.requireNonNull(name); |
|
841 return RandomGeneratorFactory.factoryOf(name, StreamableGenerator.class); |
|
842 } |
|
843 |
|
844 /** |
|
845 * Returns a {@link RandomGeneratorFactory} that can produce instances |
|
846 * of {@link StreamableGenerator} that utilizes the specified {@code algorithm}. |
|
847 * |
|
848 * @param algorithm Random number generator algorithm |
|
849 * |
|
850 * @return {@link RandomGeneratorFactory} of {@link StreamableGenerator} |
|
851 */ |
|
852 public static RandomGeneratorFactory<StreamableGenerator> factoryOf(Algorithm algorithm) { |
|
853 Objects.requireNonNull(algorithm); |
|
854 return RandomGeneratorFactory.factoryOf(algorithm.toString(), StreamableGenerator.class); |
|
855 } |
|
856 |
|
857 /** |
|
858 * Returns an effectively unlimited stream of objects, each of |
|
859 * which implements the {@link RandomGenerator} interface. Ideally the |
|
860 * generators in the stream will appear to be statistically |
|
861 * independent. The new generators should be of the same kind |
|
862 * as this generator. |
|
863 * |
|
864 * @return a stream of objects that implement the {@link RandomGenerator} interface |
|
865 * |
|
866 * @implNote It is permitted to implement this method in a manner |
|
867 * equivalent to {@code rngs(Long.MAX_VALUE)}. |
|
868 */ |
|
869 Stream<RandomGenerator> rngs(); |
|
870 |
|
871 /** |
|
872 * Returns an effectively unlimited stream of objects, each of |
|
873 * which implements the {@link RandomGenerator} interface. Ideally the |
|
874 * generators in the stream will appear to be statistically |
|
875 * independent. The new generators should be of the same kind |
|
876 * as this generator. |
|
877 * |
|
878 * @param streamSize the number of generators to generate |
|
879 * |
|
880 * @return a stream of objects that implement the {@link RandomGenerator} interface |
|
881 * |
|
882 * @throws IllegalArgumentException if {@code streamSize} is |
|
883 * less than zero |
|
884 * |
|
885 * @implNote The default implementation calls {@code rngs()} and |
|
886 * then limits its length to {@code streamSize}. |
|
887 */ |
|
888 default Stream<RandomGenerator> rngs(long streamSize) { |
|
889 RandomSupport.checkStreamSize(streamSize); |
|
890 return rngs().limit(streamSize); |
|
891 } |
|
892 } |
|
893 |
|
894 /** |
|
895 * This interface is designed to provide a common protocol for objects |
|
896 * that generate sequences of pseudorandom numbers (or Boolean values) |
|
897 * and furthermore can be <i>split</i> into two objects (the original |
|
898 * one and a new one) each of which obey that same protocol (and therefore |
|
899 * can be recursively split indefinitely). |
|
900 * <p> |
|
901 * Ideally, all {@link SplittableGenerator} objects produced by recursive |
|
902 * splitting from a single original {@link SplittableGenerator} object are |
|
903 * statistically independent of one another and individually uniform. |
|
904 * Therefore we would expect the set of values collectively generated |
|
905 * by a set of such objects to have the same statistical properties as |
|
906 * if the same quantity of values were generated by a single thread |
|
907 * using a single {@link SplittableGenerator} object. In practice, one must |
|
908 * settle for some approximation to independence and uniformity. |
|
909 * <p> |
|
910 * Methods are provided to perform a single splitting operation and |
|
911 * also to produce a stream of generators split off from the original |
|
912 * (by either iterative or recursive splitting, or a combination). |
|
913 * <p> |
|
914 * An implementation of the {@link SplittableGenerator} interface must provide |
|
915 * concrete definitions for the methods {@code nextInt()}, {@code nextLong}, |
|
916 * {@code period()}, {@code split()}, {@code split(SplittableGenerator)}, |
|
917 * {@code splits()}, {@code splits(long)}, {@code splits(SplittableGenerator)}, |
|
918 * and {@code splits(long, SplittableGenerator)}. Perhaps the most convenient |
|
919 * way to implement this interface is to extend the abstract class |
|
920 * {@link AbstractSplittableGenerator}. |
|
921 * <p> |
|
922 * Objects that implement {@link SplittableGenerator} are |
|
923 * typically not cryptographically secure. Consider instead using |
|
924 * {@link java.security.SecureRandom} to get a cryptographically |
|
925 * secure pseudo-random number generator for use by |
|
926 * security-sensitive applications. |
|
927 * |
|
928 * @since 14 |
|
929 */ |
|
930 public interface SplittableGenerator extends StreamableGenerator { |
|
931 |
|
932 /** |
|
933 * Returns an instance of {@link SplittableGenerator} that utilizes the |
|
934 * {@code name} algorithm. |
|
935 * |
|
936 * @param name Name of random number generator algorithm |
|
937 * |
|
938 * @return An instance of {@link SplittableGenerator} |
|
939 */ |
|
940 public static SplittableGenerator of(String name) { |
|
941 Objects.requireNonNull(name); |
|
942 return RandomGeneratorFactory.of(name, SplittableGenerator.class); |
|
943 } |
|
944 |
|
945 /** |
|
946 * Returns an instance of {@link SplittableGenerator} that utilizes the |
|
947 * specified {@code algorithm}. |
|
948 * |
|
949 * @param algorithm Random number generator algorithm |
|
950 * |
|
951 * @return An instance of {@link SplittableGenerator} |
|
952 */ |
|
953 public static SplittableGenerator of(Algorithm algorithm) { |
|
954 Objects.requireNonNull(algorithm); |
|
955 return RandomGeneratorFactory.of(algorithm.toString(), SplittableGenerator.class); |
|
956 } |
|
957 |
|
958 /** |
|
959 * Returns a {@link RandomGeneratorFactory} that can produce instances |
|
960 * of {@link SplittableGenerator} that utilizes the {@code name} algorithm. |
|
961 * |
|
962 * @param name Name of random number generator algorithm |
|
963 * |
|
964 * @return {@link RandomGeneratorFactory} of {@link SplittableGenerator} |
|
965 */ |
|
966 public static RandomGeneratorFactory<SplittableGenerator> factoryOf(String name) { |
|
967 Objects.requireNonNull(name); |
|
968 return RandomGeneratorFactory.factoryOf(name, SplittableGenerator.class); |
|
969 } |
|
970 |
|
971 /** |
|
972 * Returns a {@link RandomGeneratorFactory} that can produce instances |
|
973 * of {@link SplittableGenerator} that utilizes the specified {@code algorithm}. |
|
974 * |
|
975 * @param algorithm Random number generator algorithm |
|
976 * |
|
977 * @return {@link RandomGeneratorFactory} of {@link SplittableGenerator} |
|
978 */ |
|
979 public static RandomGeneratorFactory<SplittableGenerator> factoryOf(Algorithm algorithm) { |
|
980 Objects.requireNonNull(algorithm); |
|
981 return RandomGeneratorFactory.factoryOf(algorithm.toString(), SplittableGenerator.class); |
|
982 } |
|
983 |
|
984 /** |
|
985 * Returns a new pseudorandom number generator, split off from |
|
986 * this one, that implements the {@link RandomGenerator} and {@link SplittableGenerator} |
|
987 * interfaces. |
|
988 * |
|
989 * This pseudorandom number generator may be used as a source of |
|
990 * pseudorandom bits used to initialize the state the new one. |
|
991 * |
|
992 * @return a new object that implements the {@link RandomGenerator} and |
|
993 * {@link SplittableGenerator} interfaces |
|
994 */ |
|
995 SplittableGenerator split(); |
|
996 |
|
997 /** |
|
998 * Returns a new pseudorandom number generator, split off from |
|
999 * this one, that implements the {@link RandomGenerator} and {@link SplittableGenerator} |
|
1000 * interfaces. |
|
1001 * |
|
1002 * @param source a {@link SplittableGenerator} instance to be used instead |
|
1003 * of this one as a source of pseudorandom bits used to |
|
1004 * initialize the state of the new ones. |
|
1005 * |
|
1006 * @return an object that implements the {@link RandomGenerator} and |
|
1007 * {@link SplittableGenerator} interfaces |
|
1008 */ |
|
1009 SplittableGenerator split(SplittableGenerator source); |
|
1010 |
|
1011 /** |
|
1012 * Returns an effectively unlimited stream of new pseudorandom |
|
1013 * number generators, each of which implements the {@link SplittableGenerator} |
|
1014 * interface. |
|
1015 * |
|
1016 * This pseudorandom number generator may be used as a source of |
|
1017 * pseudorandom bits used to initialize the state the new ones. |
|
1018 * |
|
1019 * @implNote It is permitted to implement this method in a manner |
|
1020 * equivalent to {@code splits(Long.MAX_VALUE)}. |
|
1021 * |
|
1022 * @return a stream of {@link SplittableGenerator} objects |
|
1023 */ |
|
1024 default Stream<SplittableGenerator> splits() { |
|
1025 return this.splits(this); |
|
1026 } |
|
1027 |
|
1028 /** |
|
1029 * Returns a stream producing the given {@code streamSize} number of |
|
1030 * new pseudorandom number generators, each of which implements the |
|
1031 * {@link SplittableGenerator} interface. |
|
1032 * |
|
1033 * This pseudorandom number generator may be used as a source of |
|
1034 * pseudorandom bits used to initialize the state the new ones. |
|
1035 * |
|
1036 * @param streamSize the number of values to generate |
|
1037 * |
|
1038 * @return a stream of {@link SplittableGenerator} objects |
|
1039 * |
|
1040 * @throws IllegalArgumentException if {@code streamSize} is |
|
1041 * less than zero |
|
1042 */ |
|
1043 Stream<SplittableGenerator> splits(long streamSize); |
|
1044 |
|
1045 /** |
|
1046 * Returns an effectively unlimited stream of new pseudorandom |
|
1047 * number generators, each of which implements the {@link SplittableGenerator} |
|
1048 * interface. |
|
1049 * |
|
1050 * @param source a {@link SplittableGenerator} instance to be used instead |
|
1051 * of this one as a source of pseudorandom bits used to |
|
1052 * initialize the state of the new ones. |
|
1053 * |
|
1054 * @return a stream of {@link SplittableGenerator} objects |
|
1055 * |
|
1056 * @implNote It is permitted to implement this method in a manner |
|
1057 * equivalent to {@code splits(Long.MAX_VALUE, source)}. |
|
1058 */ |
|
1059 Stream<SplittableGenerator> splits(SplittableGenerator source); |
|
1060 |
|
1061 /** |
|
1062 * Returns a stream producing the given {@code streamSize} number of |
|
1063 * new pseudorandom number generators, each of which implements the |
|
1064 * {@link SplittableGenerator} interface. |
|
1065 * |
|
1066 * @param streamSize the number of values to generate |
|
1067 * @param source a {@link SplittableGenerator} instance to be used instead |
|
1068 * of this one as a source of pseudorandom bits used to |
|
1069 * initialize the state of the new ones. |
|
1070 * |
|
1071 * @return a stream of {@link SplittableGenerator} objects |
|
1072 * |
|
1073 * @throws IllegalArgumentException if {@code streamSize} is |
|
1074 * less than zero |
|
1075 */ |
|
1076 Stream<SplittableGenerator> splits(long streamSize, SplittableGenerator source); |
|
1077 |
|
1078 /** |
|
1079 * Returns an effectively unlimited stream of new pseudorandom |
|
1080 * number generators, each of which implements the {@link RandomGenerator} |
|
1081 * interface. Ideally the generators in the stream will appear |
|
1082 * to be statistically independent. |
|
1083 * |
|
1084 * @return a stream of objects that implement the {@link RandomGenerator} interface |
|
1085 * |
|
1086 * @implNote The default implementation calls {@code splits()}. |
|
1087 */ |
|
1088 default Stream<RandomGenerator> rngs() { |
|
1089 return this.splits().map(x -> (RandomGenerator)x); |
|
1090 } |
|
1091 |
|
1092 /** |
|
1093 * Returns a stream producing the given {@code streamSize} number of |
|
1094 * new pseudorandom number generators, each of which implements the |
|
1095 * {@link RandomGenerator} interface. Ideally the generators in the stream will |
|
1096 * appear to be statistically independent. |
|
1097 * |
|
1098 * @param streamSize the number of generators to generate |
|
1099 * |
|
1100 * @return a stream of objects that implement the {@link RandomGenerator} interface |
|
1101 * |
|
1102 * @throws IllegalArgumentException if {@code streamSize} is |
|
1103 * less than zero |
|
1104 * |
|
1105 * @implNote The default implementation calls {@code splits(streamSize)}. |
|
1106 */ |
|
1107 default Stream<RandomGenerator> rngs(long streamSize) { |
|
1108 return this.splits(streamSize).map(x -> (RandomGenerator)x); |
|
1109 } |
|
1110 } |
|
1111 |
|
1112 /** |
|
1113 * This interface is designed to provide a common protocol for objects that generate |
|
1114 * pseudorandom sequences of numbers (or Boolean values) and furthermore can easily <i>jump</i> |
|
1115 * forward (by a fixed amount) to a distant point in the state cycle. |
|
1116 * <p> |
|
1117 * Ideally, all {@link JumpableGenerator} objects produced by iterative jumping from a single |
|
1118 * original {@link JumpableGenerator} object are statistically independent of one another and |
|
1119 * individually uniform. In practice, one must settle for some approximation to independence and |
|
1120 * uniformity. In particular, a specific implementation may assume that each generator in a |
|
1121 * stream produced by the {@code jumps} method is used to produce a number of values no larger |
|
1122 * than either 2<sup>64</sup> or the square root of its period. Implementors are advised to use |
|
1123 * algorithms whose period is at least 2<sup>127</sup>. |
|
1124 * <p> |
|
1125 * Methods are provided to perform a single jump operation and also to produce a stream of |
|
1126 * generators produced from the original by iterative copying and jumping of internal state. A |
|
1127 * typical strategy for a multithreaded application is to create a single {@link |
|
1128 * JumpableGenerator} object, calls its {@code jumps} method exactly once, and then parcel out |
|
1129 * generators from the resulting stream, one to each thread. It is generally not a good idea to |
|
1130 * call {@code jump} on a generator that was itself produced by the {@code jumps} method, |
|
1131 * because the result may be a generator identical to another generator already produce by that |
|
1132 * call to the {@code jumps} method. For this reason, the return type of the {@code jumps} |
|
1133 * method is {@code Stream<RandomGenerator>} rather than {@code Stream<JumpableGenerator>}, even |
|
1134 * though the actual generator objects in that stream likely do also implement the {@link |
|
1135 * JumpableGenerator} interface. |
|
1136 * <p> |
|
1137 * An implementation of the {@link JumpableGenerator} interface must provide concrete |
|
1138 * definitions for the methods {@code nextInt()}, {@code nextLong}, {@code period()}, {@code |
|
1139 * copy()}, {@code jump()}, and {@code defaultJumpDistance()}. Default implementations are |
|
1140 * provided for all other methods. |
|
1141 * <p> |
|
1142 * Objects that implement {@link JumpableGenerator} are typically not cryptographically secure. |
|
1143 * Consider instead using {@link java.security.SecureRandom} to get a cryptographically secure |
|
1144 * pseudo-random number generator for use by security-sensitive applications. |
|
1145 * |
|
1146 * @since 14 |
|
1147 */ |
|
1148 public interface JumpableGenerator extends StreamableGenerator { |
|
1149 |
|
1150 /** |
|
1151 * Returns an instance of {@link JumpableGenerator} that utilizes the |
|
1152 * {@code name} algorithm. |
|
1153 * |
|
1154 * @param name Name of random number generator algorithm |
|
1155 * |
|
1156 * @return An instance of {@link JumpableGenerator} |
|
1157 */ |
|
1158 public static JumpableGenerator of(String name) { |
|
1159 Objects.requireNonNull(name); |
|
1160 return RandomGeneratorFactory.of(name, JumpableGenerator.class); |
|
1161 } |
|
1162 |
|
1163 /** |
|
1164 * Returns an instance of {@link JumpableGenerator} that utilizes the |
|
1165 * specified {@code algorithm}. |
|
1166 * |
|
1167 * @param algorithm Random number generator algorithm |
|
1168 * |
|
1169 * @return An instance of {@link JumpableGenerator} |
|
1170 */ |
|
1171 public static JumpableGenerator of(Algorithm algorithm) { |
|
1172 Objects.requireNonNull(algorithm); |
|
1173 return RandomGeneratorFactory.of(algorithm.toString(), JumpableGenerator.class); |
|
1174 } |
|
1175 |
|
1176 /** |
|
1177 * Returns a {@link RandomGeneratorFactory} that can produce instances |
|
1178 * of {@link JumpableGenerator} that utilizes the {@code name} algorithm. |
|
1179 * |
|
1180 * @param name Name of random number generator algorithm |
|
1181 * |
|
1182 * @return {@link RandomGeneratorFactory} of {@link JumpableGenerator} |
|
1183 */ |
|
1184 public static RandomGeneratorFactory<JumpableGenerator> factoryOf(String name) { |
|
1185 Objects.requireNonNull(name); |
|
1186 return RandomGeneratorFactory.factoryOf(name, JumpableGenerator.class); |
|
1187 } |
|
1188 |
|
1189 /** |
|
1190 * Returns a {@link RandomGeneratorFactory} that can produce instances |
|
1191 * of {@link JumpableGenerator} that utilizes the specified {@code algorithm}. |
|
1192 * |
|
1193 * @param algorithm Random number generator algorithm |
|
1194 * |
|
1195 * @return {@link RandomGeneratorFactory} of {@link JumpableGenerator} |
|
1196 */ |
|
1197 public static RandomGeneratorFactory<JumpableGenerator> factoryOf(Algorithm algorithm) { |
|
1198 Objects.requireNonNull(algorithm); |
|
1199 return RandomGeneratorFactory.factoryOf(algorithm.toString(), JumpableGenerator.class); |
|
1200 } |
|
1201 |
|
1202 /** |
|
1203 * Returns a new generator whose internal state is an exact copy of this generator (therefore |
|
1204 * their future behavior should be identical if subjected to the same series of operations). |
|
1205 * |
|
1206 * @return a new object that is a copy of this generator |
|
1207 */ |
|
1208 JumpableGenerator copy(); |
|
1209 |
|
1210 /** |
|
1211 * Alter the state of this pseudorandom number generator so as to jump forward a large, fixed |
|
1212 * distance (typically 2<sup>64</sup> or more) within its state cycle. |
|
1213 */ |
|
1214 void jump(); |
|
1215 |
|
1216 /** |
|
1217 * Returns the distance by which the {@code jump()} method will jump forward within the state |
|
1218 * cycle of this generator object. |
|
1219 * |
|
1220 * @return the default jump distance (as a {@code double} value) |
|
1221 */ |
|
1222 double defaultJumpDistance(); |
|
1223 |
|
1224 /** |
|
1225 * Returns an effectively unlimited stream of new pseudorandom number generators, each of which |
|
1226 * implements the {@link RandomGenerator} interface. |
|
1227 * |
|
1228 * @return a stream of objects that implement the {@link RandomGenerator} interface |
|
1229 * |
|
1230 * @implNote It is permitted to implement this method in a manner equivalent to |
|
1231 * {@code jumps(Long.MAX_VALUE)}. |
|
1232 * @implNote The default implementation produces a sequential stream that repeatedly |
|
1233 * calls {@code copy()} and {@code jump()} on this generator, and the copies become the |
|
1234 * generators produced by the stream. |
|
1235 */ |
|
1236 default Stream<RandomGenerator> jumps() { |
|
1237 return Stream.generate(this::copyAndJump).sequential(); |
|
1238 } |
|
1239 |
|
1240 /** |
|
1241 * Returns a stream producing the given {@code streamSize} number of new pseudorandom number |
|
1242 * generators, each of which implements the {@link RandomGenerator} interface. |
|
1243 * |
|
1244 * @param streamSize the number of generators to generate |
|
1245 * |
|
1246 * @return a stream of objects that implement the {@link RandomGenerator} interface |
|
1247 * |
|
1248 * @throws IllegalArgumentException if {@code streamSize} is less than zero |
|
1249 * @implNote The default implementation produces a sequential stream that repeatedly |
|
1250 * calls {@code copy()} and {@code jump()} on this generator, and the copies become the |
|
1251 * generators produced by the stream. |
|
1252 */ |
|
1253 default Stream<RandomGenerator> jumps(long streamSize) { |
|
1254 return jumps().limit(streamSize); |
|
1255 } |
|
1256 |
|
1257 /** |
|
1258 * Returns an effectively unlimited stream of new pseudorandom number generators, each of which |
|
1259 * implements the {@link RandomGenerator} interface. Ideally the generators in the stream |
|
1260 * will appear to be statistically independent. |
|
1261 * |
|
1262 * @return a stream of objects that implement the {@link RandomGenerator} interface |
|
1263 * |
|
1264 * @implNote The default implementation calls {@code jumps()}. |
|
1265 */ |
|
1266 default Stream<RandomGenerator> rngs() { |
|
1267 return this.jumps(); |
|
1268 } |
|
1269 |
|
1270 /** |
|
1271 * Returns a stream producing the given {@code streamSize} number of new pseudorandom number |
|
1272 * generators, each of which implements the {@link RandomGenerator} interface. Ideally |
|
1273 * the generators in the stream will appear to be statistically independent. |
|
1274 * |
|
1275 * @param streamSize the number of generators to generate |
|
1276 * |
|
1277 * @return a stream of objects that implement the {@link RandomGenerator} interface |
|
1278 * |
|
1279 * @throws IllegalArgumentException if {@code streamSize} is less than zero |
|
1280 * @implNote The default implementation calls {@code jumps(streamSize)}. |
|
1281 */ |
|
1282 default Stream<RandomGenerator> rngs(long streamSize) { |
|
1283 return this.jumps(streamSize); |
|
1284 } |
|
1285 |
|
1286 /** |
|
1287 * Copy this generator, jump this generator forward, then return the copy. |
|
1288 * |
|
1289 * @return a copy of this generator object before the jump occurred |
|
1290 */ |
|
1291 default RandomGenerator copyAndJump() { |
|
1292 RandomGenerator result = copy(); |
|
1293 jump(); |
|
1294 return result; |
|
1295 } |
|
1296 |
|
1297 } |
|
1298 |
|
1299 /** |
|
1300 * This interface is designed to provide a common protocol for objects that generate sequences |
|
1301 * of pseudorandom numbers (or Boolean values) and furthermore can easily not only jump but |
|
1302 * also |
|
1303 * <i>leap</i> to a very distant point in the state cycle. |
|
1304 * <p> |
|
1305 * Typically one will construct a series of {@link LeapableGenerator} objects by iterative |
|
1306 * leaping from a single original {@link LeapableGenerator} object, and then for each such |
|
1307 * object produce a subseries of objects by iterative jumping. There is little conceptual |
|
1308 * difference between leaping and jumping, but typically a leap will be a very long jump in the |
|
1309 * state cycle (perhaps distance 2<sup>128</sup> or so). |
|
1310 * <p> |
|
1311 * Ideally, all {@link LeapableGenerator} objects produced by iterative leaping and jumping from |
|
1312 * a single original {@link LeapableGenerator} object are statistically independent of one |
|
1313 * another and individually uniform. In practice, one must settle for some approximation to |
|
1314 * independence and uniformity. In particular, a specific implementation may assume that each |
|
1315 * generator in a stream produced by the {@code leaps} method is used to produce (by jumping) a |
|
1316 * number of objects no larger than 2<sup>64</sup>. Implementors are advised to use algorithms |
|
1317 * whose period is at least 2<sup>191</sup>. |
|
1318 * <p> |
|
1319 * Methods are provided to perform a single leap operation and also to produce a stream of |
|
1320 * generators produced from the original by iterative copying and leaping of internal state. |
|
1321 * The generators produced must implement the {@link JumpableGenerator} interface but need not |
|
1322 * also implement the {@link LeapableGenerator} interface. A typical strategy for a |
|
1323 * multithreaded application is to create a single {@link LeapableGenerator} object, calls its |
|
1324 * {@code leaps} method exactly once, and then parcel out generators from the resulting stream, |
|
1325 * one to each thread. Then the {@code jumps} method of each such generator be called to |
|
1326 * produce a substream of generator objects. |
|
1327 * <p> |
|
1328 * An implementation of the {@link LeapableGenerator} interface must provide concrete |
|
1329 * definitions for the methods {@code nextInt()}, {@code nextLong}, {@code period()}, |
|
1330 * {@code copy()}, {@code jump()}, {@code defaultJumpDistance()}, {@code leap()}, |
|
1331 * and {@code defaultLeapDistance()}. Default implementations are provided for all other |
|
1332 * methods. |
|
1333 * <p> |
|
1334 * Objects that implement {@link LeapableGenerator} are typically not cryptographically secure. |
|
1335 * Consider instead using {@link java.security.SecureRandom} to get a cryptographically secure |
|
1336 * pseudo-random number generator for use by security-sensitive applications. |
|
1337 * |
|
1338 * @since 14 |
|
1339 */ |
|
1340 public interface LeapableGenerator extends JumpableGenerator { |
|
1341 |
|
1342 /** |
|
1343 * Returns an instance of {@link LeapableGenerator} that utilizes the |
|
1344 * {@code name} algorithm. |
|
1345 * |
|
1346 * @param name Name of random number generator algorithm |
|
1347 * |
|
1348 * @return An instance of {@link LeapableGenerator} |
|
1349 */ |
|
1350 public static LeapableGenerator of(String name) { |
|
1351 Objects.requireNonNull(name); |
|
1352 return RandomGeneratorFactory.of(name, LeapableGenerator.class); |
|
1353 } |
|
1354 |
|
1355 /** |
|
1356 * Returns an instance of {@link LeapableGenerator} that utilizes the |
|
1357 * specified {@code algorithm}. |
|
1358 * |
|
1359 * @param algorithm Random number generator algorithm |
|
1360 * |
|
1361 * @return An instance of {@link LeapableGenerator} |
|
1362 */ |
|
1363 public static LeapableGenerator of(Algorithm algorithm) { |
|
1364 Objects.requireNonNull(algorithm); |
|
1365 return RandomGeneratorFactory.of(algorithm.toString(), LeapableGenerator.class); |
|
1366 } |
|
1367 |
|
1368 /** |
|
1369 * Returns a {@link RandomGeneratorFactory} that can produce instances |
|
1370 * of {@link LeapableGenerator} that utilizes the {@code name} algorithm. |
|
1371 * |
|
1372 * @param name Name of random number generator algorithm |
|
1373 * |
|
1374 * @return {@link RandomGeneratorFactory} of {@link LeapableGenerator} |
|
1375 */ |
|
1376 public static RandomGeneratorFactory<LeapableGenerator> factoryOf(String name) { |
|
1377 Objects.requireNonNull(name); |
|
1378 return RandomGeneratorFactory.factoryOf(name, LeapableGenerator.class); |
|
1379 } |
|
1380 |
|
1381 /** |
|
1382 * Returns a {@link RandomGeneratorFactory} that can produce instances |
|
1383 * of {@link LeapableGenerator} that utilizes the specified {@code algorithm}. |
|
1384 * |
|
1385 * @param algorithm Random number generator algorithm |
|
1386 * |
|
1387 * @return {@link RandomGeneratorFactory} of {@link LeapableGenerator} |
|
1388 */ |
|
1389 public static RandomGeneratorFactory<LeapableGenerator> factoryOf(Algorithm algorithm) { |
|
1390 Objects.requireNonNull(algorithm); |
|
1391 return RandomGeneratorFactory.factoryOf(algorithm.toString(), LeapableGenerator.class); |
|
1392 } |
|
1393 |
|
1394 /** |
|
1395 * Returns a new generator whose internal state is an exact copy of this generator (therefore |
|
1396 * their future behavior should be identical if subjected to the same series of operations). |
|
1397 * |
|
1398 * @return a new object that is a copy of this generator |
|
1399 */ |
|
1400 LeapableGenerator copy(); |
|
1401 |
|
1402 /** |
|
1403 * Alter the state of this pseudorandom number generator so as to leap forward a large, fixed |
|
1404 * distance (typically 2<sup>96</sup> or more) within its state cycle. |
|
1405 */ |
|
1406 void leap(); |
|
1407 |
|
1408 /** |
|
1409 * Returns the distance by which the {@code leap()} method will leap forward within the state |
|
1410 * cycle of this generator object. |
|
1411 * |
|
1412 * @return the default leap distance (as a {@code double} value) |
|
1413 */ |
|
1414 double defaultLeapDistance(); |
|
1415 |
|
1416 /** |
|
1417 * Returns an effectively unlimited stream of new pseudorandom number generators, each of which |
|
1418 * implements the {@link JumpableGenerator} interface. |
|
1419 * |
|
1420 * @return a stream of objects that implement the {@link JumpableGenerator} interface |
|
1421 * |
|
1422 * @implNote It is permitted to implement this method in a manner equivalent to {@code |
|
1423 * leaps(Long.MAX_VALUE)}. |
|
1424 * @implNote The default implementation produces a sequential stream that repeatedly |
|
1425 * calls {@code copy()} and {@code leap()} on this generator, and the copies become the |
|
1426 * generators produced by the stream. |
|
1427 */ |
|
1428 default Stream<JumpableGenerator> leaps() { |
|
1429 return Stream.generate(this::copyAndLeap).sequential(); |
|
1430 } |
|
1431 |
|
1432 /** |
|
1433 * Returns a stream producing the given {@code streamSize} number of new pseudorandom number |
|
1434 * generators, each of which implements the {@link JumpableGenerator} interface. |
|
1435 * |
|
1436 * @param streamSize the number of generators to generate |
|
1437 * |
|
1438 * @return a stream of objects that implement the {@link JumpableGenerator} interface |
|
1439 * |
|
1440 * @throws IllegalArgumentException if {@code streamSize} is less than zero |
|
1441 * @implNote The default implementation produces a sequential stream that repeatedly |
|
1442 * calls {@code copy()} and {@code leap()} on this generator, and the copies become the |
|
1443 * generators produced by the stream. |
|
1444 */ |
|
1445 default Stream<JumpableGenerator> leaps(long streamSize) { |
|
1446 return leaps().limit(streamSize); |
|
1447 } |
|
1448 |
|
1449 /** |
|
1450 * Copy this generator, leap this generator forward, then return the copy. |
|
1451 * |
|
1452 * @return a copy of this generator object before the leap occurred |
|
1453 */ |
|
1454 default JumpableGenerator copyAndLeap() { |
|
1455 JumpableGenerator result = copy(); |
|
1456 leap(); |
|
1457 return result; |
|
1458 } |
|
1459 |
|
1460 } |
|
1461 |
|
1462 /** |
|
1463 * This interface is designed to provide a common protocol for objects that generate sequences |
|
1464 * of pseudorandom numbers (or Boolean values) and furthermore can easily <i>jump</i> to an |
|
1465 * arbitrarily specified distant point in the state cycle. |
|
1466 * <p> |
|
1467 * Ideally, all {@link ArbitrarilyJumpableGenerator} objects produced by iterative jumping from |
|
1468 * a single original {@link ArbitrarilyJumpableGenerator} object are statistically independent |
|
1469 * of one another and individually uniform, provided that they do not traverse overlapping |
|
1470 * portions of the state cycle. In practice, one must settle for some approximation to |
|
1471 * independence and uniformity. In particular, a specific implementation may assume that each |
|
1472 * generator in a stream produced by the {@code jumps} method is used to produce a number of |
|
1473 * values no larger than the jump distance specified. Implementors are advised to use |
|
1474 * algorithms whose period is at least 2<sup>127</sup>. |
|
1475 * <p> |
|
1476 * For many applications, it suffices to jump forward by a power of two or some small multiple |
|
1477 * of a power of two, but this power of two may not be representable as a {@code long} value. |
|
1478 * To avoid the use of {@link java.math.BigInteger} values as jump distances, {@code double} |
|
1479 * values are used instead. |
|
1480 * <p> |
|
1481 * Methods are provided to perform a single jump operation and also to produce a stream of |
|
1482 * generators produced from the original by iterative copying and jumping of internal state. A |
|
1483 * typical strategy for a multithreaded application is to create a single |
|
1484 * {@link ArbitrarilyJumpableGenerator} object, call its {@code jumps} method exactly once, and |
|
1485 * then parcel out generators from the resulting stream, one to each thread. However, each |
|
1486 * generator produced also has type {@link ArbitrarilyJumpableGenerator}; with care, different |
|
1487 * jump distances can be used to traverse the entire state cycle in various ways. |
|
1488 * <p> |
|
1489 * An implementation of the {@link ArbitrarilyJumpableGenerator} interface must provide concrete |
|
1490 * definitions for the methods {@code nextInt()}, {@code nextLong}, {@code period()}, |
|
1491 * {@code copy()}, {@code jump(double)}, {@code defaultJumpDistance()}, and |
|
1492 * {@code defaultLeapDistance()}. Default implementations are provided for all other methods. |
|
1493 * Perhaps the most convenient way to implement this interface is to extend the abstract class |
|
1494 * {@link ArbitrarilyJumpableGenerator}, which provides spliterator-based implementations of the |
|
1495 * methods {@code ints}, {@code longs}, {@code doubles}, {@code rngs}, {@code jumps}, and |
|
1496 * {@code leaps}. |
|
1497 * <p> |
|
1498 * Objects that implement {@link ArbitrarilyJumpableGenerator} are typically not |
|
1499 * cryptographically secure. Consider instead using {@link java.security.SecureRandom} to get a |
|
1500 * cryptographically secure pseudo-random number generator for use by security-sensitive |
|
1501 * applications. |
|
1502 * |
|
1503 * @since 14 |
|
1504 */ |
|
1505 public interface ArbitrarilyJumpableGenerator extends LeapableGenerator { |
|
1506 |
|
1507 /** |
|
1508 * Returns an instance of {@link ArbitrarilyJumpableGenerator} that utilizes the |
|
1509 * {@code name} algorithm. |
|
1510 * |
|
1511 * @param name Name of random number generator algorithm |
|
1512 * |
|
1513 * @return An instance of {@link ArbitrarilyJumpableGenerator} |
|
1514 */ |
|
1515 public static ArbitrarilyJumpableGenerator of(String name) { |
|
1516 Objects.requireNonNull(name); |
|
1517 return RandomGeneratorFactory.of(name, ArbitrarilyJumpableGenerator.class); |
|
1518 } |
|
1519 |
|
1520 /** |
|
1521 * Returns an instance of {@link ArbitrarilyJumpableGenerator} that utilizes the |
|
1522 * specified {@code algorithm}. |
|
1523 * |
|
1524 * @param algorithm Random number generator algorithm |
|
1525 * |
|
1526 * @return An instance of {@link ArbitrarilyJumpableGenerator} |
|
1527 */ |
|
1528 public static ArbitrarilyJumpableGenerator of(Algorithm algorithm) { |
|
1529 Objects.requireNonNull(algorithm); |
|
1530 return RandomGeneratorFactory.of(algorithm.toString(), ArbitrarilyJumpableGenerator.class); |
|
1531 } |
|
1532 |
|
1533 /** |
|
1534 * Returns a {@link RandomGeneratorFactory} that can produce instances |
|
1535 * of {@link ArbitrarilyJumpableGenerator} that utilizes the {@code name} algorithm. |
|
1536 * |
|
1537 * @param name Name of random number generator algorithm |
|
1538 * |
|
1539 * @return {@link RandomGeneratorFactory} of {@link ArbitrarilyJumpableGenerator} |
|
1540 */ |
|
1541 public static RandomGeneratorFactory<ArbitrarilyJumpableGenerator> factoryOf(String name) { |
|
1542 Objects.requireNonNull(name); |
|
1543 return RandomGeneratorFactory.factoryOf(name, ArbitrarilyJumpableGenerator.class); |
|
1544 } |
|
1545 |
|
1546 /** |
|
1547 * Returns a {@link RandomGeneratorFactory} that can produce instances |
|
1548 * of {@link ArbitrarilyJumpableGenerator} that utilizes the specified {@code algorithm}. |
|
1549 * |
|
1550 * @param algorithm Random number generator algorithm |
|
1551 * |
|
1552 * @return {@link RandomGeneratorFactory} of {@link ArbitrarilyJumpableGenerator} |
|
1553 */ |
|
1554 public static RandomGeneratorFactory<ArbitrarilyJumpableGenerator> factoryOf(Algorithm algorithm) { |
|
1555 Objects.requireNonNull(algorithm); |
|
1556 return RandomGeneratorFactory.factoryOf(algorithm.toString(), ArbitrarilyJumpableGenerator.class); |
|
1557 } |
|
1558 |
|
1559 /** |
|
1560 * Returns a new generator whose internal state is an exact copy of this generator (therefore |
|
1561 * their future behavior should be identical if subjected to the same series of operations). |
|
1562 * |
|
1563 * @return a new object that is a copy of this generator |
|
1564 */ |
|
1565 ArbitrarilyJumpableGenerator copy(); |
|
1566 |
|
1567 /** |
|
1568 * Alter the state of this pseudorandom number generator so as to jump forward a distance equal |
|
1569 * to 2<sup>{@code logDistance}</sup> within its state cycle. |
|
1570 * |
|
1571 * @param logDistance the base-2 logarithm of the distance to jump forward within the state |
|
1572 * cycle |
|
1573 * |
|
1574 * @throws IllegalArgumentException if {@code logDistance} is NaN or negative, or if |
|
1575 * 2<sup>{@code logDistance}</sup> is greater than the period |
|
1576 * of this generator |
|
1577 */ |
|
1578 void jumpPowerOfTwo(int logDistance); |
|
1579 |
|
1580 /** |
|
1581 * Alter the state of this pseudorandom number generator so as to jump forward a specified |
|
1582 * distance within its state cycle. |
|
1583 * |
|
1584 * @param distance the distance to jump forward within the state cycle |
|
1585 * |
|
1586 * @throws IllegalArgumentException if {@code distance} is Nan, negative, or greater than the |
|
1587 * period of this generator |
|
1588 */ |
|
1589 void jump(double distance); |
|
1590 |
|
1591 /** |
|
1592 * Alter the state of this pseudorandom number generator so as to jump forward a large, fixed |
|
1593 * distance (typically 2<sup>64</sup> or more) within its state cycle. The distance used is |
|
1594 * that returned by method {@code defaultJumpDistance()}. |
|
1595 */ |
|
1596 default void jump() { jump(defaultJumpDistance()); } |
|
1597 |
|
1598 /** |
|
1599 * Returns an effectively unlimited stream of new pseudorandom number generators, each of |
|
1600 * which implements the {@link ArbitrarilyJumpableGenerator} interface, produced by jumping |
|
1601 * copies of this generator by different integer multiples of the specified jump distance. |
|
1602 * |
|
1603 * @param distance a distance to jump forward within the state cycle |
|
1604 * |
|
1605 * @return a stream of objects that implement the {@link RandomGenerator} interface |
|
1606 * |
|
1607 * @implNote This method is implemented to be equivalent to {@code jumps(Long.MAX_VALUE)}. |
|
1608 */ |
|
1609 default Stream<ArbitrarilyJumpableGenerator> jumps(double distance) { |
|
1610 return Stream.generate(() -> copyAndJump(distance)).sequential(); |
|
1611 } |
|
1612 |
|
1613 /** |
|
1614 * Returns a stream producing the given {@code streamSize} number of new pseudorandom number |
|
1615 * generators, each of which implements the {@link ArbitrarilyJumpableGenerator} interface, |
|
1616 * produced by jumping copies of this generator by different integer multiples of the |
|
1617 * specified jump distance. |
|
1618 * |
|
1619 * @param streamSize the number of generators to generate |
|
1620 * @param distance a distance to jump forward within the state cycle |
|
1621 * |
|
1622 * @return a stream of objects that implement the {@link RandomGenerator} interface |
|
1623 * |
|
1624 * @throws IllegalArgumentException if {@code streamSize} is less than zero |
|
1625 */ |
|
1626 default Stream<ArbitrarilyJumpableGenerator> jumps(long streamSize, double distance) { |
|
1627 return jumps(distance).limit(streamSize); |
|
1628 } |
|
1629 |
|
1630 /** |
|
1631 * Alter the state of this pseudorandom number generator so as to jump forward a very large, |
|
1632 * fixed distance (typically 2<sup>128</sup> or more) within its state cycle. The distance |
|
1633 * used is that returned by method {@code defaultJLeapDistance()}. |
|
1634 */ |
|
1635 default void leap() { jump(defaultLeapDistance()); } |
|
1636 |
|
1637 /** |
|
1638 * Copy this generator, jump this generator forward, then return the copy. |
|
1639 * |
|
1640 * @param distance a distance to jump forward within the state cycle |
|
1641 * |
|
1642 * @return a copy of this generator object before the jump occurred |
|
1643 */ |
|
1644 default ArbitrarilyJumpableGenerator copyAndJump(double distance) { |
|
1645 ArbitrarilyJumpableGenerator result = copy(); |
|
1646 jump(distance); |
|
1647 return result; |
|
1648 } |
|
1649 |
|
1650 } |
|
1651 } |