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    8    * particular file as subject to the "Classpath" exception as provided
    9    * by Oracle 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
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   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 section 9.6 of
   35    * <cite>The Java&trade; Language Specification</cite>.
   36    *
   37    * @author  Josh Bloch
   38    * @since   1.5
   39    */
   40   public interface Annotation {
   41       /**
   42        * Returns true if the specified object represents an annotation
   43        * that is logically equivalent to this one.  In other words,
   44        * returns true if the specified object is an instance of the same
   45        * annotation type as this instance, all of whose members are equal
   46        * to the corresponding member of this annotation, as defined below:
   47        * <ul>
   48        *    <li>Two corresponding primitive typed members whose values are
   49        *    <tt>x</tt> and <tt>y</tt> are considered equal if <tt>x == y</tt>,
   50        *    unless their type is <tt>float</tt> or <tt>double</tt>.
   51        *
   52        *    <li>Two corresponding <tt>float</tt> members whose values
   53        *    are <tt>x</tt> and <tt>y</tt> are considered equal if
   54        *    <tt>Float.valueOf(x).equals(Float.valueOf(y))</tt>.
   55        *    (Unlike the <tt>==</tt> operator, NaN is considered equal
   56        *    to itself, and <tt>0.0f</tt> unequal to <tt>-0.0f</tt>.)
   57        *
   58        *    <li>Two corresponding <tt>double</tt> members whose values
   59        *    are <tt>x</tt> and <tt>y</tt> are considered equal if
   60        *    <tt>Double.valueOf(x).equals(Double.valueOf(y))</tt>.
   61        *    (Unlike the <tt>==</tt> operator, NaN is considered equal
   62        *    to itself, and <tt>0.0</tt> unequal to <tt>-0.0</tt>.)
   63        *
   64        *    <li>Two corresponding <tt>String</tt>, <tt>Class</tt>, enum, or
   65        *    annotation typed members whose values are <tt>x</tt> and <tt>y</tt>
   66        *    are considered equal if <tt>x.equals(y)</tt>.  (Note that this
   67        *    definition is recursive for annotation typed members.)
   68        *
   69        *    <li>Two corresponding array typed members <tt>x</tt> and <tt>y</tt>
   70        *    are considered equal if <tt>Arrays.equals(x, y)</tt>, for the
   71        *    appropriate overloading of {@link java.util.Arrays#equals}.
   72        * </ul>
   73        *
   74        * @return true if the specified object represents an annotation
   75        *     that is logically equivalent to this one, otherwise false
   76        */
   77       boolean equals(Object obj);
   78   
   79       /**
   80        * Returns the hash code of this annotation, as defined below:
   81        *
   82        * <p>The hash code of an annotation is the sum of the hash codes
   83        * of its members (including those with default values), as defined
   84        * below:
   85        *
   86        * The hash code of an annotation member is (127 times the hash code
   87        * of the member-name as computed by {@link String#hashCode()}) XOR
   88        * the hash code of the member-value, as defined below:
   89        *
   90        * <p>The hash code of a member-value depends on its type:
   91        * <ul>
   92        * <li>The hash code of a primitive value <tt><i>v</i></tt> is equal to
   93        *     <tt><i>WrapperType</i>.valueOf(<i>v</i>).hashCode()</tt>, where
   94        *     <tt><i>WrapperType</i></tt> is the wrapper type corresponding
   95        *     to the primitive type of <tt><i>v</i></tt> ({@link Byte},
   96        *     {@link Character}, {@link Double}, {@link Float}, {@link Integer},
   97        *     {@link Long}, {@link Short}, or {@link Boolean}).
   98        *
   99        * <li>The hash code of a string, enum, class, or annotation member-value
  100        I     <tt><i>v</i></tt> is computed as by calling
  101        *     <tt><i>v</i>.hashCode()</tt>.  (In the case of annotation
  102        *     member values, this is a recursive definition.)
  103        *
  104        * <li>The hash code of an array member-value is computed by calling
  105        *     the appropriate overloading of
  106        *     {@link java.util.Arrays#hashCode(long[]) Arrays.hashCode}
  107        *     on the value.  (There is one overloading for each primitive
  108        *     type, and one for object reference types.)
  109        * </ul>
  110        *
  111        * @return the hash code of this annotation
  112        */
  113       int hashCode();
  114   
  115       /**
  116        * Returns a string representation of this annotation.  The details
  117        * of the representation are implementation-dependent, but the following
  118        * may be regarded as typical:
  119        * <pre>
  120        *   &#064;com.acme.util.Name(first=Alfred, middle=E., last=Neuman)
  121        * </pre>
  122        *
  123        * @return a string representation of this annotation
  124        */
  125       String toString();
  126   
  127       /**
  128        * Returns the annotation type of this annotation.
  129        */
  130       Class<? extends Annotation> annotationType();
  131   }

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