/* This file is part of the Joshua Machine Translation System.
 * 
 * Joshua 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., 59 Temple Place, Suite 330, Boston,
 * MA 02111-1307 USA
 */
package joshua.util.io;

import joshua.util.NullIterator;

import java.io.IOException;


/**
 * This class provides a null-object Reader. This is primarily
 * useful for when you may or may not have a {@link Reader}, and
 * you don't want to check for null all the time. All operations
 * are no-ops.
 *
 * @author wren ng thornton <wren@users.sourceforge.net>
 * @version $LastChangedDate: 2009-03-26 15:06:57 -0400 (Thu, 26 Mar 2009) $
 */
public class NullReader<E> extends NullIterator<E> implements Reader<E> {
	
//===============================================================
// Constructors and destructors
//===============================================================
	
	// TODO: use static factory method and singleton?
	public NullReader() { }
	
	/** A no-op. */
	public void close() throws IOException { }
	
	
//===============================================================
// Reader
//===============================================================
	
	/**
	 * Always returns true. Is this correct? What are the
	 * semantics of ready()? We're always capable of delivering
	 * nothing, but we're never capable of delivering anything...
	 */
	public boolean ready() { return true; }
	
	/** Always returns null. */
	public E readLine() throws IOException { return null; }
}