BijectiveMap.java

package kb.howtokb.utils;

import java.util.HashMap;
import java.util.Map;

/**
 * 
 * @author ntandon
 *
 * @param <K>
 * @param <V>
 */

public class BijectiveMap<K, V> extends HashMap<K, V> {

	private Map<V, K> v2k;

	public BijectiveMap() {
		super();
		v2k = new HashMap<>();
	}

	@Override
	public V put(K key, V value) {
		v2k.put(value, key);
		return super.put(key, value);
	}

	@Override
	public V remove(Object key) {

		// removing a key, implies removing the corresponding 1:1 value
		if (super.containsKey(key))
			v2k.remove(super.get(key));

		return super.remove(key);
	}

	public V getValueFromKey(K key) {
		return super.get(key);
	}

	public K getKeyFromValue(V key) {
		return v2k.get(key);
	}

	@Override
	public void putAll(Map<? extends K, ? extends V> m) {
		super.putAll(m);
	}

	@Override
	public void clear() {
		super.clear();
		v2k.clear();
	}
}