Commons Collections example source code file (TiedMapEntry.java)

This example Commons Collections source code file (TiedMapEntry.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

cannot, illegalargumentexception, io, keyvalue, map, map, object, object, serializable, serializable, string, tiedmapentry, tiedmapentry, util

The Commons Collections TiedMapEntry.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.io.Serializable;
import java.util.Map;

import org.apache.commons.collections.KeyValue;

/**
 * A {@link java.util.Map.Entry Map.Entry} tied to a map underneath.
 * <p>
 * This can be used to enable a map entry to make changes on the underlying
 * map, however this will probably mess up any iterators.
 *
 * @since Commons Collections 3.0
 * @version $Revision: 646777 $ $Date: 2008-04-10 13:33:15 +0100 (Thu, 10 Apr 2008) $
 * 
 * @author Stephen Colebourne
 */
public class TiedMapEntry implements Map.Entry, KeyValue, Serializable {

    /** Serialization version */    
    private static final long serialVersionUID = -8453869361373831205L;

    /** The map underlying the entry/iterator */    
    private final Map map;
    /** The key */
    private final Object key;

    /**
     * Constructs a new entry with the given Map and key.
     *
     * @param map  the map
     * @param key  the key
     */
    public TiedMapEntry(Map map, Object key) {
        super();
        this.map = map;
        this.key = key;
    }

    // Map.Entry interface
    //-------------------------------------------------------------------------
    /**
     * Gets the key of this entry
     * 
     * @return the key
     */
    public Object getKey() {
        return key;
    }

    /**
     * Gets the value of this entry direct from the map.
     * 
     * @return the value
     */
    public Object getValue() {
        return map.get(key);
    }

    /**
     * Sets the value associated with the key direct onto the map.
     * 
     * @param value  the new value
     * @return the old value
     * @throws IllegalArgumentException if the value is set to this map entry
     */
    public Object setValue(Object value) {
        if (value == this) {
            throw new IllegalArgumentException("Cannot set value to this map entry");
        }
        return map.put(key, value);
    }

    /**
     * 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;
        Object value = getValue();
        return
            (key == null ? other.getKey() == null : key.equals(other.getKey())) &&
            (value == null ? other.getValue() == null : value.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() {
        Object value = getValue();
        return (getKey() == null ? 0 : getKey().hashCode()) ^
               (value == null ? 0 : value.hashCode()); 
    }

    /**
     * Gets a string version of the entry.
     * 
     * @return entry as a string
     */
    public String toString() {
        return getKey() + "=" + getValue();
    }

}