73 lines
2.4 KiB
Java
73 lines
2.4 KiB
Java
/*
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* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed with
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* this work for additional information regarding copyright ownership.
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* The ASF licenses this file to You under the Apache License, Version 2.0
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* (the "License"); you may not use this file except in compliance with
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* the License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package org.apache.commons.lang3.builder;
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// adapted from org.apache.axis.utils.IDKey
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/**
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* Wrap an identity key (System.identityHashCode())
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* so that an object can only be equal() to itself.
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*
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* This is necessary to disambiguate the occasional duplicate
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* identityHashCodes that can occur.
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*/
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final class IDKey {
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private final Object value;
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private final int id;
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/**
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* Constructor for IDKey
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* @param _value The value
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*/
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IDKey(final Object _value) {
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// This is the Object hash code
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id = System.identityHashCode(_value);
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// There have been some cases (LANG-459) that return the
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// same identity hash code for different objects. So
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// the value is also added to disambiguate these cases.
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value = _value;
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}
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/**
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* returns hash code - i.e. the system identity hashcode.
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* @return the hashcode
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*/
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@Override
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public int hashCode() {
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return id;
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}
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/**
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* checks if instances are equal
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* @param other The other object to compare to
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* @return if the instances are for the same object
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*/
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@Override
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public boolean equals(final Object other) {
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if (!(other instanceof IDKey)) {
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return false;
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}
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final IDKey idKey = (IDKey) other;
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if (id != idKey.id) {
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return false;
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}
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// Note that identity equals is used.
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return value == idKey.value;
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}
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}
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