/*-
* See the file LICENSE for redistribution information.
*
* Copyright (c) 2000, 2015 Oracle and/or its affiliates. All rights reserved.
*
*/
package com.sleepycat.collections;
import java.util.Map;
/**
* A simple <code>Map.Entry</code> implementation that can be used as in
* input parameter. Since a <code>MapEntryParameter</code> is not obtained
* from a map, it is not attached to any map in particular. To emphasize that
* changing this object does not change the map, the {@link #setValue} method
* always throws <code>UnsupportedOperationException</code>.
*
* <p><b>Warning:</b> Use of this interface violates the Java Collections
* interface contract since these state that <code>Map.Entry</code> objects
* should only be obtained from <code>Map.entrySet()</code> sets, while this
* class allows constructing them directly. However, it is useful for
* performing operations on an entry set such as add(), contains(), etc. For
* restrictions see {@link #getValue} and {@link #setValue}.</p>
*
* @author Mark Hayes
*/
public class MapEntryParameter<K, V> implements Map.Entry<K, V> {
private K key;
private V value;
/**
* Creates a map entry with a given key and value.
*
* @param key is the key to use.
*
* @param value is the value to use.
*/
public MapEntryParameter(K key, V value) {
this.key = key;
this.value = value;
}
/**
* Computes a hash code as specified by {@link
* java.util.Map.Entry#hashCode}.
*
* @return the computed hash code.
*/
public int hashCode() {
return ((key == null) ? 0 : key.hashCode()) ^
((value == null) ? 0 : value.hashCode());
}
/**
* Compares this entry to a given entry as specified by {@link
* java.util.Map.Entry#equals}.
*
* @return the computed hash code.
*/
public boolean equals(Object other) {
if (!(other instanceof Map.Entry)) {
return false;
}
Map.Entry e = (Map.Entry) other;
return ((key == null) ? (e.getKey() == null)
: key.equals(e.getKey())) &&
((value == null) ? (e.getValue() == null)
: value.equals(e.getValue()));
}
/**
* Returns the key of this entry.
*
* @return the key of this entry.
*/
public final K getKey() {
return key;
}
/**
* Returns the value of this entry. Note that this will be the value
* passed to the constructor or the last value passed to {@link #setValue}.
* It will not reflect changes made to a Map.
*
* @return the value of this entry.
*/
public final V getValue() {
return value;
}
/**
* Always throws <code>UnsupportedOperationException</code> since this
* object is not attached to a map.
*/
public V setValue(V newValue) {
throw new UnsupportedOperationException();
}
final void setValueInternal(V newValue) {
this.value = newValue;
}
/**
* Converts the entry to a string representation for debugging.
*
* @return the string representation.
*/
public String toString() {
return "[key [" + key + "] value [" + value + ']';
}
}