Source for java.lang.annotation.Annotation

   1: /* Annotation.java - Base interface for all annotations
   2:    Copyright (C) 2004 Free Software Foundation
   3: 
   4: This file is part of GNU Classpath.
   5: 
   6: GNU Classpath is free software; you can redistribute it and/or modify
   7: it under the terms of the GNU General Public License as published by
   8: the Free Software Foundation; either version 2, or (at your option)
   9: any later version.
  10: 
  11: GNU Classpath is distributed in the hope that it will be useful, but
  12: WITHOUT ANY WARRANTY; without even the implied warranty of
  13: MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14: General Public License for more details.
  15: 
  16: You should have received a copy of the GNU General Public License
  17: along with GNU Classpath; see the file COPYING.  If not, write to the
  18: Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
  19: 02110-1301 USA.
  20: 
  21: Linking this library statically or dynamically with other modules is
  22: making a combined work based on this library.  Thus, the terms and
  23: conditions of the GNU General Public License cover the whole
  24: combination.
  25: 
  26: As a special exception, the copyright holders of this library give you
  27: permission to link this library with independent modules to produce an
  28: executable, regardless of the license terms of these independent
  29: modules, and to copy and distribute the resulting executable under
  30: terms of your choice, provided that you also meet, for each linked
  31: independent module, the terms and conditions of the license of that
  32: module.  An independent module is a module which is not derived from
  33: or based on this library.  If you modify this library, you may extend
  34: this exception to your version of the library, but you are not
  35: obligated to do so.  If you do not wish to do so, delete this
  36: exception statement from your version. */
  37: 
  38: package java.lang.annotation;
  39: 
  40: /**
  41:  * This is the common interface for all annotations.  Note that classes
  42:  * that implement this class manually are not classed as annotations, and
  43:  * that this interface does not define an annotation type in itself.
  44:  *
  45:  * @author Tom Tromey (tromey@redhat.com)
  46:  * @author Andrew John Hughes (gnu_andrew@member.fsf.org)
  47:  * @since 1.5
  48:  */
  49: public interface Annotation
  50: {
  51: 
  52:   /**
  53:    * Returns the type of this annotation.
  54:    *
  55:    * @return the class of which this annotation is an instance.
  56:    */
  57:   Class<? extends Annotation> annotationType();
  58: 
  59:   /**
  60:    * <p>
  61:    * Returns true if the supplied object is equivalent to this annotation.
  62:    * For this property to hold, the following must be true of <code>o</code>:
  63:    * </p>
  64:    * <ul>
  65:    * <li>The object is also an instance of the same annotation type.</li>
  66:    * <li>The members of the supplied annotation are equal to those of this
  67:    * annotation, according to the following:
  68:    * <ul>
  69:    * <li>If the members are <code>float</code>s, then, for floats
  70:    * <code>x</code> and <code>y</code>, 
  71:    * <code>Float.valueOf(x).equals(Float.valueOf(y)</code> must return
  72:    * true.  This differs from the usual (<code>==</code>) comparison
  73:    * in that <code>NaN</code> is considered equal to itself and positive
  74:    * and negative zero are seen as different.</li>
  75:    * <li>Likewise, if the members are <code>double</code>s, then, for doubles
  76:    * <code>x</code> and <code>y</code>, 
  77:    * <code>Double.valueOf(x).equals(Double.valueOf(y)</code> must return
  78:    * true.  This differs from the usual (<code>==</code>) comparison
  79:    * in that <code>NaN</code> is considered equal to itself and positive
  80:    * and negative zero are seen as different.</li>
  81:    * <li>Strings, classes, enumerations and annotations are considered
  82:    * equal according to the <code>equals()</code> implementation for these
  83:    * types.</li>
  84:    * <li>Arrays are considered equal according to <code>Arrays.equals()</code>
  85:    * </li>
  86:    * <li>Any remaining types are considered equal using <code>==</code>.</li>
  87:    * </li>
  88:    * </ul>
  89:    *
  90:    * @param o the object to compare with this annotation.
  91:    * @return true if the supplied object is an annotation with equivalent
  92:    *         members.
  93:    */
  94:   boolean equals(Object o);
  95: 
  96:   /**
  97:    * <p>
  98:    * Returns the hash code of the annotation.  This is computed as the
  99:    * 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: }