1 /* |
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2 * Copyright (c) 2012, 2013, 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 /* |
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27 * This file is available under and governed by the GNU General Public |
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28 * License version 2 only, as published by the Free Software Foundation. |
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29 * However, the following notice accompanied the original version of this |
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30 * file: |
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31 * |
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32 * Copyright (c) 2012, Stephen Colebourne & Michael Nascimento Santos |
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33 * |
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34 * All rights reserved. |
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35 * |
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36 * Redistribution and use in source and binary forms, with or without |
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37 * modification, are permitted provided that the following conditions are met: |
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38 * |
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39 * * Redistributions of source code must retain the above copyright notice, |
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40 * this list of conditions and the following disclaimer. |
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41 * |
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42 * * Redistributions in binary form must reproduce the above copyright notice, |
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43 * this list of conditions and the following disclaimer in the documentation |
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44 * and/or other materials provided with the distribution. |
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45 * |
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46 * * Neither the name of JSR-310 nor the names of its contributors |
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47 * may be used to endorse or promote products derived from this software |
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48 * without specific prior written permission. |
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49 * |
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50 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS |
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51 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT |
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52 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR |
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53 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR |
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54 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, |
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55 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, |
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56 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR |
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57 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF |
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58 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING |
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59 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS |
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60 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
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61 */ |
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62 package java.time.temporal; |
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63 |
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64 import java.time.DateTimeException; |
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65 import java.time.Duration; |
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66 import java.time.Period; |
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67 |
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68 /** |
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69 * Strategy for subtracting from a temporal object. |
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70 * <p> |
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71 * Subtractors are a key tool for modifying temporal objects. |
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72 * They exist to externalize the process of subtraction, permitting different |
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73 * approaches, as per the strategy design pattern. |
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74 * <p> |
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75 * There are two equivalent ways of using a {@code TemporalSubtractor}. |
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76 * The first is to invoke the method on this interface directly. |
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77 * The second is to use {@link Temporal#minus(TemporalSubtractor)}: |
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78 * <pre> |
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79 * // these two lines are equivalent, but the second approach is recommended |
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80 * dateTime = subtractor.subtractFrom(dateTime); |
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81 * dateTime = dateTime.minus(subtractor); |
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82 * </pre> |
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83 * It is recommended to use the second approach, {@code minus(TemporalSubtractor)}, |
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84 * as it is a lot clearer to read in code. |
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85 * <p> |
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86 * The {@link Period} and {@link Duration} classes implement this interface. |
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87 * Subtractors may also be defined by applications. |
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88 * |
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89 * <h3>Specification for implementors</h3> |
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90 * This interface places no restrictions on the mutability of implementations, |
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91 * however immutability is strongly recommended. |
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92 * |
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93 * @since 1.8 |
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94 */ |
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95 public interface TemporalSubtractor { |
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96 |
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97 /** |
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98 * Subtracts this object from the specified temporal object. |
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99 * <p> |
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100 * This adds to the specified temporal object using the logic |
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101 * encapsulated in the implementing class. |
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102 * <p> |
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103 * There are two equivalent ways of using this method. |
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104 * The first is to invoke this method directly. |
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105 * The second is to use {@link Temporal#minus(TemporalSubtractor)}: |
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106 * <pre> |
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107 * // these two lines are equivalent, but the second approach is recommended |
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108 * dateTime = subtractor.subtractFrom(dateTime); |
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109 * dateTime = dateTime.minus(subtractor); |
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110 * </pre> |
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111 * It is recommended to use the second approach, {@code minus(TemporalSubtractor)}, |
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112 * as it is a lot clearer to read in code. |
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113 * |
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114 * <h3>Specification for implementors</h3> |
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115 * The implementation must take the input object and subtract from it. |
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116 * The implementation defines the logic of the subtraction and is responsible for |
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117 * documenting that logic. It may use any method on {@code Temporal} to |
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118 * query the temporal object and perform the subtraction. |
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119 * The returned object must have the same observable type as the input object |
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120 * <p> |
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121 * The input object must not be altered. |
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122 * Instead, an adjusted copy of the original must be returned. |
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123 * This provides equivalent, safe behavior for immutable and mutable temporal objects. |
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124 * <p> |
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125 * The input temporal object may be in a calendar system other than ISO. |
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126 * Implementations may choose to document compatibility with other calendar systems, |
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127 * or reject non-ISO temporal objects by {@link Queries#chrono() querying the chronology}. |
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128 * <p> |
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129 * This method may be called from multiple threads in parallel. |
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130 * It must be thread-safe when invoked. |
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131 * |
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132 * @param temporal the temporal object to adjust, not null |
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133 * @return an object of the same observable type with the subtraction made, not null |
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134 * @throws DateTimeException if unable to subtract |
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135 * @throws ArithmeticException if numeric overflow occurs |
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136 */ |
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137 Temporal subtractFrom(Temporal temporal); |
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138 |
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139 } |
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