Current set
/*
* Copyright Ben Meadowcroft 2006
* Version: $Revision: 1.1 $
* Date: $Date: 2006/02/24 22:24:46 $
*/
//com.agnotion.util.concurrent;
import java.util.Collection;
import java.util.Iterator;
import java.util.Set;
import java.util.concurrent.ConcurrentHashMap;
/**
* @author Ben Meadowcroft
*/
public class ConcurrentSet<Q> implements Set<Q>
{
/** Piggy back off a concurrent hash map to get "weekly consistent" iterators etc */
private ConcurrentHashMap<Q, Object> map = new ConcurrentHashMap<Q, Object>();
/**
*
*/
public ConcurrentSet() {
this.map = new ConcurrentHashMap<Q, Object>();
}
/* (non-Javadoc)
* @see java.util.Set#add(E)
*/
public boolean add(Q item) {
boolean containsObj = map.containsKey(item);
if (containsObj == false)
{
/* ConcurrentHashMap doesn't allow null keys or values so we simply
* use the item added to the collection as the key and the Boolean
* TRUE object as the value. */
map.put(item, Boolean.TRUE);
}
return !containsObj;
}
/* (non-Javadoc)
* @see java.util.Set#addAll(java.util.Collection)
*/
public boolean addAll(Collection<? extends Q> items) {
boolean changed = false;
for (Q item : items)
{
/* update flag determining whether set has changed or not */
changed = add(item) || changed;
}
return changed;
}
/* (non-Javadoc)
* @see java.util.Set#clear()
*/
public void clear() {
map.clear();
}
/* (non-Javadoc)
* @see java.util.Set#contains(java.lang.Object)
*/
public boolean contains(Object item) {
return map.containsKey(item);
}
/* (non-Javadoc)
* @see java.util.Set#containsAll(java.util.Collection)
*/
public boolean containsAll(Collection<?> items) {
return map.keySet().containsAll(items);
}
/* (non-Javadoc)
* @see java.util.Set#isEmpty()
*/
public boolean isEmpty() {
return map.isEmpty();
}
/* (non-Javadoc)
* @see java.util.Set#iterator()
*/
public Iterator<Q> iterator() {
return map.keySet().iterator();
}
/* (non-Javadoc)
* @see java.util.Set#remove(java.lang.Object)
*/
public boolean remove(Object item) {
/* we double up argument as both key and value */
return map.remove(item, Boolean.TRUE);
}
/* (non-Javadoc)
* @see java.util.Set#removeAll(java.util.Collection)
*/
public boolean removeAll(Collection<?> items) {
return map.keySet().removeAll(items);
}
/* (non-Javadoc)
* @see java.util.Set#retainAll(java.util.Collection)
*/
public boolean retainAll(Collection<?> items) {
return map.keySet().retainAll(items);
}
/* (non-Javadoc)
* @see java.util.Set#size()
*/
public int size() {
return map.size();
}
/* (non-Javadoc)
* @see java.util.Set#toArray()
*/
public Object[] toArray() {
return map.keySet().toArray();
}
/* (non-Javadoc)
* @see java.util.Set#toArray(T[])
*/
public <T> T[] toArray(T[] array) {
return map.keySet().toArray(array);
}
}
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