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1 /* |
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2 * Copyright (c) 2003, 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 package java.lang.annotation; |
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27 |
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28 /** |
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29 * The common interface extended by all annotation types. Note that an |
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30 * interface that manually extends this one does <i>not</i> define |
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31 * an annotation type. Also note that this interface does not itself |
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32 * define an annotation type. |
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33 * |
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34 * More information about annotation types can be found in section 9.6 of |
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35 * <cite>The Java™ Language Specification</cite>. |
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36 * |
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37 * The {@link java.lang.reflect.AnnotatedElement} interface discusses |
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38 * compatibility concerns when evolving an annotation type from being |
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39 * non-repeatable to being repeatable. |
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40 * |
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41 * @author Josh Bloch |
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42 * @since 1.5 |
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43 */ |
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44 public interface Annotation { |
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45 /** |
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46 * Returns true if the specified object represents an annotation |
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47 * that is logically equivalent to this one. In other words, |
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48 * returns true if the specified object is an instance of the same |
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49 * annotation type as this instance, all of whose members are equal |
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50 * to the corresponding member of this annotation, as defined below: |
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51 * <ul> |
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52 * <li>Two corresponding primitive typed members whose values are |
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53 * <tt>x</tt> and <tt>y</tt> are considered equal if <tt>x == y</tt>, |
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54 * unless their type is <tt>float</tt> or <tt>double</tt>. |
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55 * |
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56 * <li>Two corresponding <tt>float</tt> members whose values |
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57 * are <tt>x</tt> and <tt>y</tt> are considered equal if |
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58 * <tt>Float.valueOf(x).equals(Float.valueOf(y))</tt>. |
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59 * (Unlike the <tt>==</tt> operator, NaN is considered equal |
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60 * to itself, and <tt>0.0f</tt> unequal to <tt>-0.0f</tt>.) |
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61 * |
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62 * <li>Two corresponding <tt>double</tt> members whose values |
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63 * are <tt>x</tt> and <tt>y</tt> are considered equal if |
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64 * <tt>Double.valueOf(x).equals(Double.valueOf(y))</tt>. |
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65 * (Unlike the <tt>==</tt> operator, NaN is considered equal |
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66 * to itself, and <tt>0.0</tt> unequal to <tt>-0.0</tt>.) |
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67 * |
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68 * <li>Two corresponding <tt>String</tt>, <tt>Class</tt>, enum, or |
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69 * annotation typed members whose values are <tt>x</tt> and <tt>y</tt> |
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70 * are considered equal if <tt>x.equals(y)</tt>. (Note that this |
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71 * definition is recursive for annotation typed members.) |
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72 * |
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73 * <li>Two corresponding array typed members <tt>x</tt> and <tt>y</tt> |
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74 * are considered equal if <tt>Arrays.equals(x, y)</tt>, for the |
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75 * appropriate overloading of {@link java.util.Arrays#equals}. |
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76 * </ul> |
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77 * |
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78 * @return true if the specified object represents an annotation |
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79 * that is logically equivalent to this one, otherwise false |
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80 */ |
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81 boolean equals(Object obj); |
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82 |
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83 /** |
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84 * Returns the hash code of this annotation, as defined below: |
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85 * |
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86 * <p>The hash code of an annotation is the sum of the hash codes |
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87 * of its members (including those with default values), as defined |
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88 * below: |
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89 * |
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90 * The hash code of an annotation member is (127 times the hash code |
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91 * of the member-name as computed by {@link String#hashCode()}) XOR |
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92 * the hash code of the member-value, as defined below: |
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93 * |
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94 * <p>The hash code of a member-value depends on its type: |
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95 * <ul> |
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96 * <li>The hash code of a primitive value <tt><i>v</i></tt> is equal to |
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97 * <tt><i>WrapperType</i>.valueOf(<i>v</i>).hashCode()</tt>, where |
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98 * <tt><i>WrapperType</i></tt> is the wrapper type corresponding |
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99 * to the primitive type of <tt><i>v</i></tt> ({@link Byte}, |
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100 * {@link Character}, {@link Double}, {@link Float}, {@link Integer}, |
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101 * {@link Long}, {@link Short}, or {@link Boolean}). |
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102 * |
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103 * <li>The hash code of a string, enum, class, or annotation member-value |
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104 I <tt><i>v</i></tt> is computed as by calling |
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105 * <tt><i>v</i>.hashCode()</tt>. (In the case of annotation |
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106 * member values, this is a recursive definition.) |
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107 * |
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108 * <li>The hash code of an array member-value is computed by calling |
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109 * the appropriate overloading of |
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110 * {@link java.util.Arrays#hashCode(long[]) Arrays.hashCode} |
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111 * on the value. (There is one overloading for each primitive |
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112 * type, and one for object reference types.) |
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113 * </ul> |
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114 * |
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115 * @return the hash code of this annotation |
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116 */ |
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117 int hashCode(); |
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118 |
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119 /** |
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120 * Returns a string representation of this annotation. The details |
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121 * of the representation are implementation-dependent, but the following |
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122 * may be regarded as typical: |
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123 * <pre> |
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124 * @com.acme.util.Name(first=Alfred, middle=E., last=Neuman) |
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125 * </pre> |
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126 * |
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127 * @return a string representation of this annotation |
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128 */ |
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129 String toString(); |
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130 |
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131 /** |
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132 * Returns the annotation type of this annotation. |
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133 * @return the annotation type of this annotation |
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134 */ |
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135 Class<? extends Annotation> annotationType(); |
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136 } |