001 /* 002 * Licensed to the Apache Software Foundation (ASF) under one or more 003 * contributor license agreements. See the NOTICE file distributed with 004 * this work for additional information regarding copyright ownership. 005 * The ASF licenses this file to You under the Apache License, Version 2.0 006 * (the "License"); you may not use this file except in compliance with 007 * the License. You may obtain a copy of the License at 008 * 009 * http://www.apache.org/licenses/LICENSE-2.0 010 * 011 * Unless required by applicable law or agreed to in writing, software 012 * distributed under the License is distributed on an "AS IS" BASIS, 013 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 014 * See the License for the specific language governing permissions and 015 * limitations under the License. 016 */ 017 package org.apache.commons.collections.keyvalue; 018 019 import java.util.Map; 020 021 /** 022 * Abstract Pair class to assist with creating correct 023 * {@link java.util.Map.Entry Map.Entry} implementations. 024 * 025 * @since Commons Collections 3.0 026 * @version $Revision: 646777 $ $Date: 2008-04-10 13:33:15 +0100 (Thu, 10 Apr 2008) $ 027 * 028 * @author James Strachan 029 * @author Michael A. Smith 030 * @author Neil O'Toole 031 * @author Stephen Colebourne 032 */ 033 public abstract class AbstractMapEntry extends AbstractKeyValue implements Map.Entry { 034 035 /** 036 * Constructs a new entry with the given key and given value. 037 * 038 * @param key the key for the entry, may be null 039 * @param value the value for the entry, may be null 040 */ 041 protected AbstractMapEntry(Object key, Object value) { 042 super(key, value); 043 } 044 045 // Map.Entry interface 046 //------------------------------------------------------------------------- 047 /** 048 * Sets the value stored in this <code>Map.Entry</code>. 049 * <p> 050 * This <code>Map.Entry</code> is not connected to a Map, so only the 051 * local data is changed. 052 * 053 * @param value the new value 054 * @return the previous value 055 */ 056 public Object setValue(Object value) { 057 Object answer = this.value; 058 this.value = value; 059 return answer; 060 } 061 062 /** 063 * Compares this <code>Map.Entry</code> with another <code>Map.Entry</code>. 064 * <p> 065 * Implemented per API documentation of {@link java.util.Map.Entry#equals(Object)} 066 * 067 * @param obj the object to compare to 068 * @return true if equal key and value 069 */ 070 public boolean equals(Object obj) { 071 if (obj == this) { 072 return true; 073 } 074 if (obj instanceof Map.Entry == false) { 075 return false; 076 } 077 Map.Entry other = (Map.Entry) obj; 078 return 079 (getKey() == null ? other.getKey() == null : getKey().equals(other.getKey())) && 080 (getValue() == null ? other.getValue() == null : getValue().equals(other.getValue())); 081 } 082 083 /** 084 * Gets a hashCode compatible with the equals method. 085 * <p> 086 * Implemented per API documentation of {@link java.util.Map.Entry#hashCode()} 087 * 088 * @return a suitable hash code 089 */ 090 public int hashCode() { 091 return (getKey() == null ? 0 : getKey().hashCode()) ^ 092 (getValue() == null ? 0 : getValue().hashCode()); 093 } 094 095 }