com.groupbyinc.common.apache.commons.collections4.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.collections4.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 3.1
* @version $Id: MapBackedSet.java 1686855 2015-06-22 13:00:27Z tn $
*/
public final class MapBackedSet implements Set, Serializable {
/** Serialization version */
private static final long serialVersionUID = 6723912213766056587L;
/** The map being used as the backing store */
private final Map map;
/** The dummyValue to use */
private final V dummyValue;
/**
* Factory method to create a set from a map.
*
* @param the element type
* @param the dummy value type in the map
* @param map the map to decorate, must not be null
* @return a new map backed set
* @throws NullPointerException if map is null
* @since 4.0
*/
public static MapBackedSet mapBackedSet(final Map map) {
return mapBackedSet(map, null);
}
/**
* Factory method to create a set from a map.
*
* @param the element type
* @param the dummy value type in the map
* @param map the map to decorate, must not be null
* @param dummyValue the dummy value to use
* @return a new map backed set
* @throws NullPointerException if map is null
* @since 4.0
*/
public static MapBackedSet mapBackedSet(final Map map, final V dummyValue) {
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 NullPointerException if map is null
*/
private MapBackedSet(final Map map, final V dummyValue) {
super();
if (map == null) {
throw new NullPointerException("The map must not be null");
}
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(final Object obj) {
return map.containsKey(obj);
}
public boolean containsAll(final Collection coll) {
return map.keySet().containsAll(coll);
}
public boolean add(final E obj) {
final int size = map.size();
map.put(obj, dummyValue);
return map.size() != size;
}
public boolean addAll(final Collection coll) {
final int size = map.size();
for (final E e : coll) {
map.put(e, dummyValue);
}
return map.size() != size;
}
public boolean remove(final Object obj) {
final int size = map.size();
map.remove(obj);
return map.size() != size;
}
public boolean removeAll(final Collection coll) {
return map.keySet().removeAll(coll);
}
public boolean retainAll(final Collection coll) {
return map.keySet().retainAll(coll);
}
public void clear() {
map.clear();
}
public Object[] toArray() {
return map.keySet().toArray();
}
public T[] toArray(final T[] array) {
return map.keySet().toArray(array);
}
@Override
public boolean equals(final Object obj) {
return map.keySet().equals(obj);
}
@Override
public int hashCode() {
return map.keySet().hashCode();
}
}