1 /*

     2  * Copyright (c) 2017, 2017, Oracle and/or its affiliates. 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.  Oracle designates this

     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

    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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

    22  * or visit www.oracle.com if you need additional information or have any

    23  * questions.

    24  */

    25 package org.graalvm.collections;

    26 

    27 /**

    28  * Strategy for comparing two objects. Default predefined strategies are {@link #DEFAULT},

    29  * {@link #IDENTITY}, and {@link #IDENTITY_WITH_SYSTEM_HASHCODE}.

    30  *

    31  * @since 1.0

    32  */

    33 public abstract class Equivalence {

    34 

    35     /**

    36      * Default equivalence calling {@link #equals(Object)} to check equality and {@link #hashCode()}

    37      * for obtaining hash values. Do not change the logic of this class as it may be inlined in

    38      * other places.

    39      *

    40      * @since 1.0

    41      */

    42     public static final Equivalence DEFAULT = new Equivalence() {

    43 

    44         @Override

    45         public boolean equals(Object a, Object b) {

    46             return a.equals(b);

    47         }

    48 

    49         @Override

    50         public int hashCode(Object o) {

    51             return o.hashCode();

    52         }

    53     };

    54 

    55     /**

    56      * Identity equivalence using {@code ==} to check equality and {@link #hashCode()} for obtaining

    57      * hash values. Do not change the logic of this class as it may be inlined in other places.

    58      *

    59      * @since 1.0

    60      */

    61     public static final Equivalence IDENTITY = new Equivalence() {

    62 

    63         @Override

    64         public boolean equals(Object a, Object b) {

    65             return a == b;

    66         }

    67 

    68         @Override

    69         public int hashCode(Object o) {

    70             return o.hashCode();

    71         }

    72     };

    73 

    74     /**

    75      * Identity equivalence using {@code ==} to check equality and

    76      * {@link System#identityHashCode(Object)} for obtaining hash values. Do not change the logic of

    77      * this class as it may be inlined in other places.

    78      *

    79      * @since 1.0

    80      */

    81     public static final Equivalence IDENTITY_WITH_SYSTEM_HASHCODE = new Equivalence() {

    82 

    83         @Override

    84         public boolean equals(Object a, Object b) {

    85             return a == b;

    86         }

    87 

    88         @Override

    89         public int hashCode(Object o) {

    90             return System.identityHashCode(o);

    91         }

    92     };

    93 

    94     /**

    95      * Subclass for creating custom equivalence definitions.

    96      *

    97      * @since 1.0

    98      */

    99     protected Equivalence() {

   100     }

   101 

   102     /**

   103      * Returns {@code true} if the non-{@code null} arguments are equal to each other and

   104      * {@code false} otherwise.

   105      *

   106      * @since 1.0

   107      */

   108     public abstract boolean equals(Object a, Object b);

   109 

   110     /**

   111      * Returns the hash code of a non-{@code null} argument {@code o}.

   112      *

   113      * @since 1.0

   114      */

   115     public abstract int hashCode(Object o);

   116 }