/*

  * Licensed to the Apache Software Foundation (ASF) under one or more

  * contributor license agreements.  See the NOTICE file distributed with

  * this work for additional information regarding copyright ownership.

  * The ASF licenses this file to You under the Apache License, Version 2.0

  * (the "License"); you may not use this file except in compliance with

  * the License.  You may obtain a copy of the License at

  *

  *   http://www.apache.org/licenses/LICENSE-2.0

  *

  * Unless required by applicable law or agreed to in writing, software

  * distributed under the License is distributed on an "AS IS" BASIS,

  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

  * See the License for the specific language governing permissions and

  * limitations under the License.

  * 

  */

 package org.apache.commons.lang3.builder;

 // adapted from org.apache.axis.utils.IDKey

 /**

  * Wrap an identity key (System.identityHashCode()) 

  * so that an object can only be equal() to itself.

  * 

  * This is necessary to disambiguate the occasional duplicate

  * identityHashCodes that can occur.

  * 

  */ 

 final class IDKey {

         private final Object value;

         private final int id;

         /**

          * Constructor for IDKey

          * @param _value The value

          */ 

         public IDKey(final Object _value) {

             // This is the Object hashcode 

             id = System.identityHashCode(_value);  

             // There have been some cases (LANG-459) that return the 

             // same identity hash code for different objects.  So 

             // the value is also added to disambiguate these cases.

             value = _value;

         }

         /**

          * returns hashcode - i.e. the system identity hashcode.

          * @return the hashcode

          */ 

         @Override

         public int hashCode() {

            return id;

         }

         /**

          * checks if instances are equal

          * @param other The other object to compare to

          * @return if the instances are for the same object

          */ 

         @Override

         public boolean equals(final Object other) {

             if (!(other instanceof IDKey)) {

                 return false;

             }

             final IDKey idKey = (IDKey) other;

             if (id != idKey.id) {

                 return false;

             }

             // Note that identity equals is used.

             return value == idKey.value;

          }

 }