jodd.util.collection.SetMapAdapter Maven / Gradle / Ivy
// Copyright (c) 2003-present, Jodd Team (http://jodd.org)
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package jodd.util.collection;
import java.util.AbstractSet;
import java.util.Iterator;
import java.util.Map;
/**
* Map adapter for a set provides an easy way to have a Set from various map implementations.
*/
public abstract class SetMapAdapter extends AbstractSet {
protected Map map;
// Dummy value to associate with an Object in the backing Map
private static final Object DUMMY_VALUE = new Object();
/**
* Constructs a new, empty set; the backing HashMap instance has
* default initial capacity (16) and load factor (0.75).
*/
protected SetMapAdapter(final Map mapImplementation) {
this.map = mapImplementation;
}
/**
* 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.
*/
@Override
public Iterator iterator() {
return map.keySet().iterator();
}
/**
* Returns the number of elements in this set (its cardinality).
*/
@Override
public int size() {
return map.size();
}
/**
* Returns true if this set contains no elements.
*/
@Override
public boolean isEmpty() {
return map.isEmpty();
}
/**
* Returns true if this set contains the specified element.
*
* @param o element whose presence in this set is to be tested.
* @return true if this set contains the specified element.
*/
@SuppressWarnings({"SuspiciousMethodCalls"})
@Override
public boolean contains(final Object o) {
return map.containsKey(o);
}
/**
* Adds the specified element to this set if it is not already
* present.
*
* @param o element to be added to this set.
* @return true if the set did not already contain the specified
* element.
*/
@Override
public boolean add(final E o) {
return map.put(o, DUMMY_VALUE) == null;
}
/**
* Removes the specified element from this set if it is present.
*
* @param o object to be removed from this set, if present.
* @return true if the set contained the specified element.
*/
@Override
public boolean remove(final Object o) {
return map.remove(o) == DUMMY_VALUE;
}
/**
* Removes all of the elements from this set.
*/
@Override
public void clear() {
map.clear();
}
}