ReversableHashtable.java

package ptolemy.actor.ptalon.model;

import java.util.Hashtable;
import java.util.Map;

public class ReversableHashtable<K, V> extends Hashtable<K, V> {
	private Hashtable<V, K> reverse = new Hashtable<V, K>();
	
	public synchronized void clear() {
		reverse.clear();
		super.clear();
	}
	
	public synchronized K getKey(V value) {
		return reverse.get(value);
	}
	
	public synchronized V put(K key, V value) {
		if (reverse.containsKey(value)) {
			throw new IllegalArgumentException(
					"Cannot put key, value pair, since the value is a duplicate.");
		}
		reverse.put(value, key);
		return super.put(key, value);
	}
	
	public synchronized void putAll(Map<? extends K, ? extends V> t) {
		throw new UnsupportedOperationException(
				"putAll() is not supported in this inherited class.");
	}
	
	public synchronized V remove(Object key) {
		V value = super.remove(key);
		reverse.remove(value);
		return value;
	}
	
	public boolean containsValue(Object value) {
		return reverse.containsKey(value);
	}
}