/*

 * 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

         */

        IDKey(final Object _value) {

            // This is the Object hash code

            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 hash code - 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;

         }

}