package org.infinispan.commons.util.concurrent;
import java.io.Serializable;
import java.util.AbstractSet;
import java.util.Collection;
import java.util.Iterator;
import java.util.concurrent.ConcurrentMap;
import org.infinispan.commons.util.CollectionFactory;
/**
* A simple Set implementation backed by a {@link java.util.concurrent.ConcurrentHashMap} to deal with the fact that the
* JDK does not have a proper concurrent Set implementation that uses efficient lock striping.
* <p/>
* Note that values are stored as keys in the underlying Map, with a static dummy object as value.
*
* @author <a href="mailto:manik@jboss.org">Manik Surtani</a>
* @since 4.0
*/
public class ConcurrentHashSet<E> extends AbstractSet<E> implements Serializable {
/**
* The serialVersionUID
*/
private static final long serialVersionUID = 5312604953511379869L;
/**
* any Serializable object will do, Integer.valueOf(0) is known cheap
**/
private static final Serializable DUMMY = 0;
protected final ConcurrentMap<E, Object> map;
public ConcurrentHashSet() {
map = CollectionFactory.makeConcurrentMap();
}
/**
* @param concurrencyLevel passed in to the underlying CHM. See {@link java.util.concurrent.ConcurrentHashMap#ConcurrentHashMap(int,
* float, int)} javadocs for details.
*/
public ConcurrentHashSet(int concurrencyLevel) {
map = CollectionFactory.makeConcurrentMap(16, concurrencyLevel);
}
/**
* Params passed in to the underlying CHM. See {@link java.util.concurrent.ConcurrentHashMap#ConcurrentHashMap(int,
* float, int)} javadocs for details.
*/
public ConcurrentHashSet(int initSize, float loadFactor, int concurrencyLevel) {
map = CollectionFactory.makeConcurrentMap(initSize, loadFactor, concurrencyLevel);
}
@Override
public int size() {
return map.size();
}
@Override
public boolean isEmpty() {
return map.isEmpty();
}
@Override
public boolean contains(Object o) {
return map.containsKey(o);
}
@Override
public Iterator<E> iterator() {
return map.keySet().iterator();
}
@Override
public Object[] toArray() {
return map.keySet().toArray();
}
@Override
public <T> T[] toArray(T[] a) {
return map.keySet().toArray(a);
}
@Override
public boolean add(E o) {
Object v = map.put(o, DUMMY);
return v == null;
}
@Override
public boolean remove(Object o) {
Object v = map.remove(o);
return v != null;
}
@Override
public boolean containsAll(Collection<?> c) {
return map.keySet().containsAll(c);
}
@Override
public boolean addAll(Collection<? extends E> c) {
throw new UnsupportedOperationException("Not supported in this implementation since additional locking is required and cannot directly be delegated to multiple calls to ConcurrentHashMap");
}
@Override
public boolean retainAll(Collection<?> c) {
throw new UnsupportedOperationException("Not supported in this implementation since additional locking is required and cannot directly be delegated to multiple calls to ConcurrentHashMap");
}
@Override
public boolean removeAll(Collection<?> c) {
throw new UnsupportedOperationException("Not supported in this implementation since additional locking is required and cannot directly be delegated to multiple calls to ConcurrentHashMap");
}
@Override
public void clear() {
map.clear();
}
}