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Commons Collections example source code file (AbstractMapEntry.java)

This example Commons Collections source code file (AbstractMapEntry.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - Commons Collections tags/keywords

abstractkeyvalue, abstractkeyvalue, abstractmapentry, abstractmapentry, object, object, util

The Commons Collections AbstractMapEntry.java source code

/*
 *  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.collections.keyvalue;

import java.util.Map;

/**
 * Abstract Pair class to assist with creating correct
 * {@link java.util.Map.Entry Map.Entry} implementations.
 *
 * @since Commons Collections 3.0
 * @version $Revision: 646777 $ $Date: 2008-04-10 13:33:15 +0100 (Thu, 10 Apr 2008) $
 * 
 * @author James Strachan
 * @author Michael A. Smith
 * @author Neil O'Toole
 * @author Stephen Colebourne
 */
public abstract class AbstractMapEntry extends AbstractKeyValue implements Map.Entry {

    /**
     * Constructs a new entry with the given key and given value.
     *
     * @param key  the key for the entry, may be null
     * @param value  the value for the entry, may be null
     */
    protected AbstractMapEntry(Object key, Object value) {
        super(key, value);
    }

    // Map.Entry interface
    //-------------------------------------------------------------------------
    /** 
     * Sets the value stored in this <code>Map.Entry.
     * <p>
     * This <code>Map.Entry is not connected to a Map, so only the
     * local data is changed.
     *
     * @param value  the new value
     * @return the previous value
     */
    public Object setValue(Object value) {
        Object answer = this.value;
        this.value = value;
        return answer;
    }

    /**
     * Compares this <code>Map.Entry with another Map.Entry.
     * <p>
     * Implemented per API documentation of {@link java.util.Map.Entry#equals(Object)}
     * 
     * @param obj  the object to compare to
     * @return true if equal key and value
     */
    public boolean equals(Object obj) {
        if (obj == this) {
            return true;
        }
        if (obj instanceof Map.Entry == false) {
            return false;
        }
        Map.Entry other = (Map.Entry) obj;
        return
            (getKey() == null ? other.getKey() == null : getKey().equals(other.getKey())) &&
            (getValue() == null ? other.getValue() == null : getValue().equals(other.getValue()));
    }

    /**
     * Gets a hashCode compatible with the equals method.
     * <p>
     * Implemented per API documentation of {@link java.util.Map.Entry#hashCode()}
     * 
     * @return a suitable hash code
     */
    public int hashCode() {
        return (getKey() == null ? 0 : getKey().hashCode()) ^
               (getValue() == null ? 0 : getValue().hashCode()); 
    }

}

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