AbstractIterator.java

/*
 * Copyright © 2012-2013 The University of Texas at Dallas
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package edu.utdallas.cs.stormrider.store.iterator;

import java.util.ArrayList;
import java.util.HashSet;
import java.util.List;
import java.util.NoSuchElementException;
import java.util.Set;

import com.hp.hpl.jena.util.iterator.NiceIterator;

public abstract class AbstractIterator<T> extends NiceIterator<T> 
{
	private T obj = null;
	
	@Override
	public void close() {}

	public abstract T _next() ;
	
	@Override
	public boolean hasNext() 
	{
		if( obj == null ) obj = _next() ;
		return obj != null ;
	}

	@Override
	public T next() 
	{
		if( obj == null ) { obj = _next() ; if( obj == null ) { throw new NoSuchElementException() ; } }
		T result = obj ; obj = null ; return result ;
	}

	@Override
	public void remove() { throw new UnsupportedOperationException() ; }

	@Override
	public T removeNext() { throw new UnsupportedOperationException() ; }

	@Override
	public List<T> toList() 
	{
		List<T> list = new ArrayList<T>() ;
		while( hasNext() ) { list.add( next() ) ; }
		return list ;
	}

	@Override
	public Set<T> toSet() 
	{
		Set<T> set = new HashSet<T>() ;
		while( hasNext() ) { set.add( next() ) ; }
		return set ;
	}
}