FilteredCollection.java

/*
 * GNU LESSER GENERAL PUBLIC LICENSE Copyright (C) 2006 The Lobo Project
 * 
 * This library is free software; you can redistribute it and/or modify it under
 * the terms of the GNU Lesser General Public License as published by the Free
 * Software Foundation; either version 2.1 of the License, or (at your option)
 * any later version.
 * 
 * This library is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
 * FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more
 * details.
 * 
 * You should have received a copy of the GNU Lesser General Public License
 * along with this library; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
 * 
 * Contact info: lobochief@users.sourceforge.net
 */
/*
 * Created on Oct 8, 2005
 */
package com.nvarghese.beowulf.common.cobra.util;

import java.util.ArrayList;
import java.util.Collection;
import java.util.Iterator;
import java.util.NoSuchElementException;

public class FilteredCollection implements Collection {

	private final ObjectFilter filter;
	private final Collection sourceCollection;

	public FilteredCollection(final Collection sourceCollection, final ObjectFilter filter) {

		this.filter = filter;
		this.sourceCollection = sourceCollection;
	}

	public int size() {

		int count = 0;
		Iterator i = this.sourceCollection.iterator();
		while (i.hasNext()) {
			if (this.filter.decode(i.next()) != null) {
				count++;
			}
		}
		return count;
	}

	public boolean isEmpty() {

		Iterator i = this.sourceCollection.iterator();
		while (i.hasNext()) {
			if (this.filter.decode(i.next()) != null) {
				return false;
			}
		}
		return true;
	}

	public boolean contains(final Object o) {

		return this.sourceCollection.contains(this.filter.encode(o));
	}

	public Iterator iterator() {

		final Iterator sourceIterator = this.sourceCollection.iterator();
		return new Iterator() {

			private Boolean hasNext;
			private Object next;

			private void scanNext() {

				while (sourceIterator.hasNext()) {
					Object item = filter.decode(sourceIterator.next());
					if (item != null) {
						hasNext = Boolean.TRUE;
						this.next = item;
					}
				}
				hasNext = Boolean.FALSE;
			}

			/*
			 * (non-Javadoc)
			 * 
			 * @see java.util.Iterator#hasNext()
			 */
			public boolean hasNext() {

				if (this.hasNext == null) {
					scanNext();
				}
				return this.hasNext.booleanValue();
			}

			/*
			 * (non-Javadoc)
			 * 
			 * @see java.util.Iterator#next()
			 */
			public Object next() {

				if (this.hasNext == null) {
					scanNext();
				}
				if (Boolean.FALSE.equals(this.hasNext)) {
					throw new NoSuchElementException();
				}
				Object next = this.next;
				this.hasNext = null;
				return next;
			}

			/*
			 * (non-Javadoc)
			 * 
			 * @see java.util.Iterator#remove()
			 */
			public void remove() {

				throw new UnsupportedOperationException();
			}
		};
	}

	public Object[] toArray() {

		return this.toArray(new Object[0]);
	}

	public Object[] toArray(final Object[] a) {

		Collection bucket = new ArrayList();
		Iterator i = this.sourceCollection.iterator();
		while (i.hasNext()) {
			Object item = this.filter.decode(i.next());
			if (item != null) {
				bucket.add(item);
			}
		}
		return bucket.toArray(a);
	}

	public boolean add(final Object o) {

		return this.sourceCollection.add(this.filter.encode(o));
	}

	public boolean remove(final Object o) {

		return this.sourceCollection.remove(this.filter.encode(o));
	}

	public boolean containsAll(final Collection c) {

		Iterator i = c.iterator();
		while (i.hasNext()) {
			if (!this.contains(i.next())) {
				return false;
			}
		}
		return true;
	}

	public boolean addAll(final Collection c) {

		boolean result = false;
		Iterator i = c.iterator();
		while (i.hasNext()) {
			if (this.add(i.next())) {
				result = true;
			}
		}
		return result;
	}

	public boolean removeAll(final Collection c) {

		boolean result = false;
		Iterator i = c.iterator();
		while (i.hasNext()) {
			if (this.remove(i.next())) {
				result = true;
			}
		}
		return result;
	}

	public boolean retainAll(final Collection c) {

		boolean result = false;
		Object[] values = this.toArray();
		for (int i = 0; i < values.length; i++) {
			if (!c.contains(values[i])) {
				if (this.remove(values[i])) {
					result = true;
				}
			}
		}
		return result;
	}

	public void clear() {

		Object[] values = this.toArray();
		for (int i = 0; i < values.length; i++) {
			this.sourceCollection.remove(this.filter.encode(values[i]));
		}
	}
}