ThreadSafeHashMap.java

import java.util.Collection;
import java.util.Collections;
import java.util.HashMap;
import java.util.LinkedHashMap;
import java.util.Map;
import java.util.Map.Entry;
import java.util.Set;

/**
 * スレッドセーフな{@link HashMap}です。
 */
public class ThreadSafeHashMap<K, V> extends HashMap<K, V> {

  /**
	 * <code>serialVersionUID</code>
	 */
	private static final long serialVersionUID = 1L;

	private Map<K, V> delegated = Collections
			.synchronizedMap(new HashMap<K, V>());

	@Override
	public int size() {
		return delegated.size();
	}

	@Override
	public boolean isEmpty() {
		return delegated.isEmpty();
	}

	@Override
	public boolean containsKey(Object key) {
		return delegated.containsKey(key);
	}

	@Override
	public boolean containsValue(Object value) {
		return delegated.containsValue(value);
	}

	@Override
	public V get(Object key) {
		return delegated.get(key);
	}

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

	@Override
	public V remove(Object key) {
		return delegated.remove(key);
	}

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

	@Override
	public void clear() {
		delegated.clear();
	}

	@Override
	public Set<K> keySet() {
		return delegated.keySet();
	}

	@Override
	public Collection<V> values() {
		return delegated.values();
	}

	@Override
	public boolean equals(Object o) {
		return delegated.equals(o);
	}

	@Override
	public int hashCode() {
		return delegated.hashCode();
	}

	/**
	 * {@link java.util.HashMap}のwriteObjectメソッドがスレッドセーフでないため、インスタンスをコピーして
	 * {@link Set}を返しています。
	 * 
	 * @return entrtySet
	 * @see java.util.HashMap#entrySet()
	 */
	@Override
	public Set<Map.Entry<K, V>> entrySet() {
		synchronized (delegated) {
			Set<Entry<K, V>> set = new LinkedHashMap<K, V>(delegated)
					.entrySet();
			return set;
		}

	}

}