org.apache.commons.lang3.builder.IDKey Maven / Gradle / Ivy
/*
* 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;
}
}