1 /*
2 * Copyright 2003-2009 Sun Microsystems, Inc. All Rights Reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation. Sun designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Sun in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
22 * CA 95054 USA or visit www.sun.com if you need additional information or
23 * have any questions.
24 */
25
26 package java.lang.annotation;
27
28 /**
29 * The common interface extended by all annotation types. Note that an
30 * interface that manually extends this one does <i>not</i> define
31 * an annotation type. Also note that this interface does not itself
32 * define an annotation type.
33 *
34 * More information about annotation types can be found in <i>The
35 * Java™ Language Specification, Third Edition</i>, <a
36 * href="http://java.sun.com/docs/books/jls/third_edition/html/interfaces.html#9.6">§9.6</a>.
37 *
38 * @author Josh Bloch
39 * @since 1.5
40 */
41 public interface Annotation {
42 /**
43 * Returns true if the specified object represents an annotation
44 * that is logically equivalent to this one. In other words,
45 * returns true if the specified object is an instance of the same
46 * annotation type as this instance, all of whose members are equal
47 * to the corresponding member of this annotation, as defined below:
48 * <ul>
49 * <li>Two corresponding primitive typed members whose values are
50 * <tt>x</tt> and <tt>y</tt> are considered equal if <tt>x == y</tt>,
51 * unless their type is <tt>float</tt> or <tt>double</tt>.
52 *
53 * <li>Two corresponding <tt>float</tt> members whose values
54 * are <tt>x</tt> and <tt>y</tt> are considered equal if
55 * <tt>Float.valueOf(x).equals(Float.valueOf(y))</tt>.
56 * (Unlike the <tt>==</tt> operator, NaN is considered equal
57 * to itself, and <tt>0.0f</tt> unequal to <tt>-0.0f</tt>.)
58 *
59 * <li>Two corresponding <tt>double</tt> members whose values
60 * are <tt>x</tt> and <tt>y</tt> are considered equal if
61 * <tt>Double.valueOf(x).equals(Double.valueOf(y))</tt>.
62 * (Unlike the <tt>==</tt> operator, NaN is considered equal
63 * to itself, and <tt>0.0</tt> unequal to <tt>-0.0</tt>.)
64 *
65 * <li>Two corresponding <tt>String</tt>, <tt>Class</tt>, enum, or
66 * annotation typed members whose values are <tt>x</tt> and <tt>y</tt>
67 * are considered equal if <tt>x.equals(y)</tt>. (Note that this
68 * definition is recursive for annotation typed members.)
69 *
70 * <li>Two corresponding array typed members <tt>x</tt> and <tt>y</tt>
71 * are considered equal if <tt>Arrays.equals(x, y)</tt>, for the
72 * appropriate overloading of {@link java.util.Arrays#equals}.
73 * </ul>
74 *
75 * @return true if the specified object represents an annotation
76 * that is logically equivalent to this one, otherwise false
77 */
78 boolean equals(Object obj);
79
80 /**
81 * Returns the hash code of this annotation, as defined below:
82 *
83 * <p>The hash code of an annotation is the sum of the hash codes
84 * of its members (including those with default values), as defined
85 * below:
86 *
87 * The hash code of an annotation member is (127 times the hash code
88 * of the member-name as computed by {@link String#hashCode()}) XOR
89 * the hash code of the member-value, as defined below:
90 *
91 * <p>The hash code of a member-value depends on its type:
92 * <ul>
93 * <li>The hash code of a primitive value <tt><i>v</i></tt> is equal to
94 * <tt><i>WrapperType</i>.valueOf(<i>v</i>).hashCode()</tt>, where
95 * <tt><i>WrapperType</i></tt> is the wrapper type corresponding
96 * to the primitive type of <tt><i>v</i></tt> ({@link Byte},
97 * {@link Character}, {@link Double}, {@link Float}, {@link Integer},
98 * {@link Long}, {@link Short}, or {@link Boolean}).
99 *
100 * <li>The hash code of a string, enum, class, or annotation member-value
101 I <tt><i>v</i></tt> is computed as by calling
102 * <tt><i>v</i>.hashCode()</tt>. (In the case of annotation
103 * member values, this is a recursive definition.)
104 *
105 * <li>The hash code of an array member-value is computed by calling
106 * the appropriate overloading of
107 * {@link java.util.Arrays#hashCode(long[]) Arrays.hashCode}
108 * on the value. (There is one overloading for each primitive
109 * type, and one for object reference types.)
110 * </ul>
111 *
112 * @return the hash code of this annotation
113 */
114 int hashCode();
115
116 /**
117 * Returns a string representation of this annotation. The details
118 * of the representation are implementation-dependent, but the following
119 * may be regarded as typical:
120 * <pre>
121 * @com.acme.util.Name(first=Alfred, middle=E., last=Neuman)
122 * </pre>
123 *
124 * @return a string representation of this annotation
125 */
126 String toString();
127
128 /**
129 * Returns the annotation type of this annotation.
130 */
131 Class<? extends Annotation> annotationType();
132 }