com.github.lontime.extcommons.lang3.ConcurrentHashSet Maven / Gradle / Ivy
package com.github.lontime.extcommons.lang3;
import java.util.AbstractSet;
import java.util.ConcurrentModificationException;
import java.util.Iterator;
import java.util.Set;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;
/**
* ConcurrentHashSet.
* @author lontime
* @since 1.0
*/
public class ConcurrentHashSet extends AbstractSet implements Set, java.io.Serializable {
private static final long serialVersionUID = -8672117787651310382L;
private static final Object PRESENT = new Object();
private final ConcurrentMap map;
public ConcurrentHashSet() {
map = new ConcurrentHashMap<>();
}
public ConcurrentHashSet(int initialCapacity) {
map = new ConcurrentHashMap(initialCapacity);
}
/**
* Returns an iterator over the elements in this set. The elements are
* returned in no particular order.
*
* @return an Iterator over the elements in this set
* @see ConcurrentModificationException
*/
@Override
public Iterator iterator() {
return map.keySet().iterator();
}
/**
* Returns the number of elements in this set (its cardinality).
*
* @return the number of elements in this set (its cardinality)
*/
@Override
public int size() {
return map.size();
}
/**
* Returns true if this set contains no elements.
*
* @return true if this set contains no elements
*/
@Override
public boolean isEmpty() {
return map.isEmpty();
}
/**
* Returns true if this set contains the specified element. More
* formally, returns true if and only if this set contains an
* element e such that
* (o==null ? e==null : o.equals(e)).
*
* @param o element whose presence in this set is to be tested
* @return true if this set contains the specified element
*/
@Override
public boolean contains(Object o) {
return map.containsKey(o);
}
/**
* Adds the specified element to this set if it is not already present. More
* formally, adds the specified element e to this set if this set
* contains no element e2 such that
* (e==null ? e2==null : e.equals(e2)). If this
* set already contains the element, the call leaves the set unchanged and
* returns false.
*
* @param e element to be added to this set
* @return true if this set did not already contain the specified
* element
*/
@Override
public boolean add(E e) {
return map.put(e, PRESENT) == null;
}
/**
* addIfAbsent.
* @param e element
* @return true/false
*/
public boolean addIfAbsent(E e) {
return map.putIfAbsent(e, PRESENT) == null;
}
/**
* Removes the specified element from this set if it is present. More
* formally, removes an element e such that
* (o==null ? e==null : o.equals(e)), if this
* set contains such an element. Returns true if this set contained
* the element (or equivalently, if this set changed as a result of the
* call). (This set will not contain the element once the call returns.)
*
* @param o object to be removed from this set, if present
* @return true if the set contained the specified element
*/
@Override
public boolean remove(Object o) {
return map.remove(o) == PRESENT;
}
/**
* Removes all of the elements from this set. The set will be empty after
* this call returns.
*/
@Override
public void clear() {
map.clear();
}
}