org.apache.commons.collections.set.MapBackedSet Maven / Gradle / Ivy
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You under the Apache License, Version 2.0
* (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.commons.collections.set;
import java.io.Serializable;
import java.util.Collection;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;
/**
* Decorates a Map to obtain Set behaviour.
*
* This class is used to create a Set with the same properties as
* the key set of any map. Thus, a ReferenceSet can be created by wrapping a
* ReferenceMap in an instance of this class.
*
* Most map implementation can be used to create a set by passing in dummy values.
* Exceptions include BidiMap implementations, as they require unique values.
*
* @since Commons Collections 3.1
* @version $Revision: 646777 $ $Date: 2008-04-10 14:33:15 +0200 (Thu, 10 Apr 2008) $
*
* @author Stephen Colebourne
*/
public final class MapBackedSet implements Set, Serializable {
/** Serialization version */
private static final long serialVersionUID = 6723912213766056587L;
/** The map being used as the backing store */
protected final Map map;
/** The dummyValue to use */
protected final Object dummyValue;
/**
* Factory method to create a set from a map.
*
* @param map the map to decorate, must not be null
* @throws IllegalArgumentException if set is null
*/
public static Set decorate(Map map) {
return decorate(map, null);
}
/**
* Factory method to create a set from a map.
*
* @param map the map to decorate, must not be null
* @param dummyValue the dummy value to use
* @throws IllegalArgumentException if map is null
*/
public static Set decorate(Map map, Object dummyValue) {
if (map == null) {
throw new IllegalArgumentException("The map must not be null");
}
return new MapBackedSet(map, dummyValue);
}
//-----------------------------------------------------------------------
/**
* Constructor that wraps (not copies).
*
* @param map the map to decorate, must not be null
* @param dummyValue the dummy value to use
* @throws IllegalArgumentException if map is null
*/
private MapBackedSet(Map map, Object dummyValue) {
super();
this.map = map;
this.dummyValue = dummyValue;
}
//-----------------------------------------------------------------------
public int size() {
return map.size();
}
public boolean isEmpty() {
return map.isEmpty();
}
public Iterator iterator() {
return map.keySet().iterator();
}
public boolean contains(Object obj) {
return map.containsKey(obj);
}
public boolean containsAll(Collection coll) {
return map.keySet().containsAll(coll);
}
public boolean add(Object obj) {
int size = map.size();
map.put(obj, dummyValue);
return (map.size() != size);
}
public boolean addAll(Collection coll) {
int size = map.size();
for (Iterator it = coll.iterator(); it.hasNext();) {
Object obj = it.next();
map.put(obj, dummyValue);
}
return (map.size() != size);
}
public boolean remove(Object obj) {
int size = map.size();
map.remove(obj);
return (map.size() != size);
}
public boolean removeAll(Collection coll) {
return map.keySet().removeAll(coll);
}
public boolean retainAll(Collection coll) {
return map.keySet().retainAll(coll);
}
public void clear() {
map.clear();
}
public Object[] toArray() {
return map.keySet().toArray();
}
public Object[] toArray(Object[] array) {
return map.keySet().toArray(array);
}
public boolean equals(Object obj) {
return map.keySet().equals(obj);
}
public int hashCode() {
return map.keySet().hashCode();
}
}