identitymap.java

用Java实现的23个常用设计模式源代码

//$Id: IdentityMap.java,v 1.6.2.6 2003/11/29 07:55:15 oneovthafew Exp $
package net.sf.hibernate.util;

import java.io.Serializable;
import java.util.ArrayList;
import java.util.Collection;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Set;

import org.apache.commons.collections.SequencedHashMap;

/**
 * A <tt>Map</tt> where keys are compared by object identity,
 * rather than <tt>equals()</tt>.
 */

public final class IdentityMap implements Map {
	
	/**
	 * Return a new instance of this class, with an undefined
	 * iteration order
	 * 
	 * @return Map
	 */
	public static Map instantiate(int size) {
		return new IdentityMap( new HashMap(size) );
	}
	
	/**
	 * Return a new instance of this class, with iteration
	 * order defined by the order that entries were added
	 */
	public static Map instantiateSequenced(int size) {
		return new IdentityMap( new SequencedHashMap(size) );
	}
	
	private IdentityMap(Map underlyingMap) {
		map = underlyingMap;
	}
	
	/**
	 * Return the map entries (as instances of <tt>Map.Entry</tt> in a collection that
	 * is safe from concurrent modification). ie. we may safely add new instances to
	 * the underlying <tt>Map</tt> during iteration of the <tt>entries()</tt>.
	 * 
	 * @param map
	 * @return Collection
	 */
	public static List concurrentEntries(Map map) {
		return ( (IdentityMap) map ).entryList();
	}

	public static List entries(Map map) {
		return ( (IdentityMap) map ).entryList();
	}
	
	public static Iterator keyIterator(Map map) {
		return ( (IdentityMap) map ).keyIterator();
	}
	
	public Iterator keyIterator() {
		return new KeyIterator( map.keySet().iterator() );
	}
	
	private final Map map;
	
	public static final class IdentityMapEntry implements java.util.Map.Entry {
		IdentityMapEntry(Object key, Object value) {
			this.key=key;
			this.value=value;
		}
		private Object key;
		private Object value;
		public Object getKey() {
			return key;
		}
		
		public Object getValue() {
			return value;
		}
		
		public Object setValue(Object value) {
			Object result = this.value;
			this.value = value;
			return result;
		}
	}
	
	public static final class IdentityKey implements Serializable {
		private Object key;
		
		IdentityKey(Object key) {
			this.key=key;
		}
		public boolean equals(Object other) {
			return key == ( (IdentityKey) other ).key;
		}
		public int hashCode() {
			return System.identityHashCode(key);
		}
	}

	public int size() {
		return map.size();
	}
	
	public boolean isEmpty() {
		return map.isEmpty();
	}
	
	public boolean containsKey(Object key) {
		IdentityKey k = new IdentityKey(key);
		return map.containsKey(k);
	}
	
	public boolean containsValue(Object val) {
		return map.containsValue(val);
	}
	
	public Object get(Object key) {
		IdentityKey k = new IdentityKey(key);
		return map.get(k);
	}
	
	public Object put(Object key, Object value) {
		return map.put( new IdentityKey(key), value );
	}
	
	public Object remove(Object key) {
		IdentityKey k = new IdentityKey(key);
		return map.remove(k);
	}
	
	public void putAll(Map otherMap) {
		Iterator iter = otherMap.entrySet().iterator();
		while ( iter.hasNext() ) {
			Map.Entry me = (Map.Entry) iter.next();
			put( me.getKey(), me.getValue() );
		}
	}
	
	public void clear() {
		map.clear();
	}
	
	public Set keySet() {
		// would need an IdentitySet for this!
		throw new UnsupportedOperationException();
	}
	
	public Collection values() {
		return map.values();
	}
	
	public Set entrySet() {
		Set set = new HashSet( map.size() );
		Iterator iter = map.entrySet().iterator();
		while ( iter.hasNext() ) {
			Map.Entry me = (Map.Entry) iter.next();
			set.add( new IdentityMapEntry( ( (IdentityKey) me.getKey() ).key, me.getValue() ) );
		}
		return set;
	}

	public List entryList() {
		ArrayList list = new ArrayList( map.size() );
		Iterator iter = map.entrySet().iterator();
		while ( iter.hasNext() ) {
			Map.Entry me = (Map.Entry) iter.next();
			list.add( new IdentityMapEntry( ( (IdentityKey) me.getKey() ).key, me.getValue() ) );
		}
		return list;
	}
	
	/**
	 * Workaround for a JDK 1.4.1 bug where <tt>IdentityHashMap</tt>s are not 
	 * correctly deserialized.
	 * 
	 * @param map
	 * @return Object
	 */
	public static Object serialize(Map map) {
		return ( (IdentityMap) map ).map;
	}
	
	/**
	 * Workaround for a JDK 1.4.1 bug where <tt>IdentityHashMap</tt>s are not 
	 * correctly deserialized.
	 * 
	 * @param o
	 * @return Map
	 */
	public static Map deserialize(Object o) {
		return new IdentityMap( (Map) o );
	}
	
	static final class KeyIterator implements Iterator {
		
		private KeyIterator(Iterator iter) {
			identityKeyIterator = iter;
		}
		
		private final Iterator identityKeyIterator;

		public boolean hasNext() {
			return identityKeyIterator.hasNext();
		}

		public Object next() {
			return ( (IdentityKey) identityKeyIterator.next() ).key;
		}

		public void remove() {
			throw new UnsupportedOperationException();
		}

}
}