import java.util.Collection;
import java.util.Map;
import java.util.HashMap;
import java.util.Iterator;

public class GettableHashSet<E> implements GettableSet<E> {
	
	private Map<E, E> map;
	
	public GettableHashSet() {
		this(16);
	}
	
	public GettableHashSet(Collection<? extends E> coll) {
		this(coll.size());
		addAll(coll);
	}
	
	public GettableHashSet(int initialCapacity) {
		this(initialCapacity, 0.75f);
	}
	
	public GettableHashSet(int initialCapacity, float loadFactor) {
		map = new HashMap<E, E>(initialCapacity, loadFactor);
	}
	
	public E get(E obj) {
		return map.get(obj);
	}
	
	public int size() {
		return map.keySet().size();
	}
	
	public boolean isEmpty() {
		return map.isEmpty();
	}
	
	public void clear() {
		map.clear();
	}
	
	/**
	Note that calling this will replace any equal object currently in the set.
	*/
	public boolean add(E obj) {
		if (obj == null) throw new NullPointerException("null elements not supported"); // ban null to make computation of the return value a bit easier
		return map.put(obj, obj) == null;
	}
	
	// if you don't want replacement, either use this, or replace the normal add() with it
	public boolean addWithoutReplacing(E obj) {
		if (obj == null) throw new NullPointerException("null elements not supported"); // ban null to make computation of the return value a bit easier
		if (!map.containsKey(obj)) {
			map.put(obj, obj);
			return true;
		}
		else {
			return false;
		}
	}
	
	public boolean addAll(Collection<? extends E> coll) {
		boolean changed = false;
		for (E obj: coll) {
			changed = changed | add(obj);
		}
		return changed;
	}
	
	public boolean remove(Object obj) {
		return map.keySet().remove(obj);
	}
	
	public boolean removeAll(Collection<?> coll) {
		return map.keySet().removeAll(coll);
	}
	
	public boolean retainAll(Collection<?> coll) {
		return map.keySet().retainAll(coll);
	}
	
	public boolean contains(Object obj) {
		return map.containsKey(obj);
	}
	
	public boolean containsAll(Collection<?> coll) {
		return map.keySet().containsAll(coll);
	}
	
	public <T> T[] toArray(T[] arr) {
		return map.keySet().toArray(arr);
	}
	
	public Object[] toArray() {
		return map.keySet().toArray();
	}
	
	public Iterator<E> iterator() {
		return map.keySet().iterator();
	}
	
}