001 /* Annotation.java - Base interface for all annotations 002 Copyright (C) 2004 Free Software Foundation 003 004 This file is part of GNU Classpath. 005 006 GNU Classpath is free software; you can redistribute it and/or modify 007 it under the terms of the GNU General Public License as published by 008 the Free Software Foundation; either version 2, or (at your option) 009 any later version. 010 011 GNU Classpath is distributed in the hope that it will be useful, but 012 WITHOUT ANY WARRANTY; without even the implied warranty of 013 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 014 General Public License for more details. 015 016 You should have received a copy of the GNU General Public License 017 along with GNU Classpath; see the file COPYING. If not, write to the 018 Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 019 02110-1301 USA. 020 021 Linking this library statically or dynamically with other modules is 022 making a combined work based on this library. Thus, the terms and 023 conditions of the GNU General Public License cover the whole 024 combination. 025 026 As a special exception, the copyright holders of this library give you 027 permission to link this library with independent modules to produce an 028 executable, regardless of the license terms of these independent 029 modules, and to copy and distribute the resulting executable under 030 terms of your choice, provided that you also meet, for each linked 031 independent module, the terms and conditions of the license of that 032 module. An independent module is a module which is not derived from 033 or based on this library. If you modify this library, you may extend 034 this exception to your version of the library, but you are not 035 obligated to do so. If you do not wish to do so, delete this 036 exception statement from your version. */ 037 038 package java.lang.annotation; 039 040 /** 041 * This is the common interface for all annotations. Note that classes 042 * that implement this class manually are not classed as annotations, and 043 * that this interface does not define an annotation type in itself. 044 * 045 * @author Tom Tromey (tromey@redhat.com) 046 * @author Andrew John Hughes (gnu_andrew@member.fsf.org) 047 * @since 1.5 048 */ 049 public interface Annotation 050 { 051 052 /** 053 * Returns the type of this annotation. 054 * 055 * @return the class of which this annotation is an instance. 056 */ 057 Class<? extends Annotation> annotationType(); 058 059 /** 060 * <p> 061 * Returns true if the supplied object is equivalent to this annotation. 062 * For this property to hold, the following must be true of <code>o</code>: 063 * </p> 064 * <ul> 065 * <li>The object is also an instance of the same annotation type.</li> 066 * <li>The members of the supplied annotation are equal to those of this 067 * annotation, according to the following: 068 * <ul> 069 * <li>If the members are <code>float</code>s, then, for floats 070 * <code>x</code> and <code>y</code>, 071 * <code>Float.valueOf(x).equals(Float.valueOf(y)</code> must return 072 * true. This differs from the usual (<code>==</code>) comparison 073 * in that <code>NaN</code> is considered equal to itself and positive 074 * and negative zero are seen as different.</li> 075 * <li>Likewise, if the members are <code>double</code>s, then, for doubles 076 * <code>x</code> and <code>y</code>, 077 * <code>Double.valueOf(x).equals(Double.valueOf(y)</code> must return 078 * true. This differs from the usual (<code>==</code>) comparison 079 * in that <code>NaN</code> is considered equal to itself and positive 080 * and negative zero are seen as different.</li> 081 * <li>Strings, classes, enumerations and annotations are considered 082 * equal according to the <code>equals()</code> implementation for these 083 * types.</li> 084 * <li>Arrays are considered equal according to <code>Arrays.equals()</code> 085 * </li> 086 * <li>Any remaining types are considered equal using <code>==</code>.</li> 087 * </li> 088 * </ul> 089 * 090 * @param o the object to compare with this annotation. 091 * @return true if the supplied object is an annotation with equivalent 092 * members. 093 */ 094 boolean equals(Object o); 095 096 /** 097 * <p> 098 * Returns the hash code of the annotation. This is computed as the 099 * sum of the hash codes of the annotation's members. 100 * </p> 101 * <p> 102 * The hash code of a member of the annotation is the result of XORing 103 * the hash code of its value with the result of multiplying the hash code 104 * of its name by 127. Formally, if the value is <code>v</code> and the 105 * name is <code>n</code>, the hash code of the member is 106 * v.hashCode() XOR (127 * String.hashCode(n)). <code>v.hashCode()</code> 107 * is defined as follows: 108 * </p> 109 * <ul> 110 * <li>The hash code of a primitive value (i.e. <code>byte</code>, 111 * <code>char</code>, <code>double</code>, <code>float</code>, 112 * <code>int</code>, <code>long</code>, <code>short</code> and 113 * <code>boolean</code>) is the hash code obtained from its corresponding 114 * wrapper class using <code>valueOf(v).hashCode()</code>, where 115 * <code>v</code> is the primitive value.</li> 116 * <li>The hash code of an enumeration, string, class or other annotation 117 * is obtained using <code>v.hashCode()</code>.</li> 118 * <li>The hash code of an array is computed using 119 * <code>Arrays.hashCode(v)</code>.</li> 120 * </ul> 121 * 122 * @return the hash code of the annotation, computed as the sum of its 123 * member hashcodes. 124 */ 125 int hashCode(); 126 127 /** 128 * Returns a textual representation of the annotation. This is 129 * implementation-dependent, but is expected to include the classname 130 * and the names and values of each member. 131 * 132 * @return a textual representation of the annotation. 133 */ 134 String toString(); 135 }