/*
* Copyright 2003-2006 The Apache Software Foundation
*
* Licensed 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;
import org.apache.commons.collections.KeyValue;
/**
* A mutable <code>KeyValue</code> pair that does not implement
* {@link java.util.Map.Entry Map.Entry}.
* <p>
* Note that a <code>DefaultKeyValue</code> instance may not contain
* itself as a key or value.
*
* @since Commons Collections 3.0
* @version $Revision: 405927 $ $Date: 2006-05-12 23:57:03 +0100 (Fri, 12 May 2006) $
*
* @author James Strachan
* @author Michael A. Smith
* @author Neil O'Toole
* @author Stephen Colebourne
*/
public class DefaultKeyValue extends AbstractKeyValue {
/**
* Constructs a new pair with a null key and null value.
*/
public DefaultKeyValue() {
super(null, null);
}
/**
* Constructs a new pair with the specified key and given value.
*
* @param key the key for the entry, may be null
* @param value the value for the entry, may be null
*/
public DefaultKeyValue(final Object key, final Object value) {
super(key, value);
}
/**
* Constructs a new pair from the specified <code>KeyValue</code>.
*
* @param pair the pair to copy, must not be null
* @throws NullPointerException if the entry is null
*/
public DefaultKeyValue(final KeyValue pair) {
super(pair.getKey(), pair.getValue());
}
/**
* Constructs a new pair from the specified <code>Map.Entry</code>.
*
* @param entry the entry to copy, must not be null
* @throws NullPointerException if the entry is null
*/
public DefaultKeyValue(final Map.Entry entry) {
super(entry.getKey(), entry.getValue());
}
//-----------------------------------------------------------------------
/**
* Sets the key.
*
* @param key the new key
* @return the old key
* @throws IllegalArgumentException if key is this object
*/
public Object setKey(final Object key) {
if (key == this) {
throw new IllegalArgumentException("DefaultKeyValue may not contain itself as a key.");
}
final Object old = this.key;
this.key = key;
return old;
}
/**
* Sets the value.
*
* @return the old value of the value
* @param value the new value
* @throws IllegalArgumentException if value is this object
*/
public Object setValue(final Object value) {
if (value == this) {
throw new IllegalArgumentException("DefaultKeyValue may not contain itself as a value.");
}
final Object old = this.value;
this.value = value;
return old;
}
//-----------------------------------------------------------------------
/**
* Returns a new <code>Map.Entry</code> object with key and value from this pair.
*
* @return a MapEntry instance
*/
public Map.Entry toMapEntry() {
return new DefaultMapEntry(this);
}
//-----------------------------------------------------------------------
/**
* Compares this <code>Map.Entry</code> with another <code>Map.Entry</code>.
* <p>
* Returns true if the compared object is also a <code>DefaultKeyValue</code>,
* and its key and value are equal to this object's key and value.
*
* @param obj the object to compare to
* @return true if equal key and value
*/
public boolean equals(final Object obj) {
if (obj == this) {
return true;
}
if (obj instanceof DefaultKeyValue == false) {
return false;
}
DefaultKeyValue other = (DefaultKeyValue) 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()},
* however subclasses may override this.
*
* @return a suitable hash code
*/
public int hashCode() {
return (getKey() == null ? 0 : getKey().hashCode()) ^
(getValue() == null ? 0 : getValue().hashCode());
}
}