/*******************************************************************************
*   Copyright 2014 Analog Devices, Inc.
*
*   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 com.analog.lyric.collect;

import org.eclipse.jdt.annotation.Nullable;

import com.google.common.collect.UnmodifiableIterator;

/**
 * An iterator that returns a single value.
 * <p>
 * Unlike Guava's {@link com.google.common.collect.Iterators#singletonIterator}
 * this implementation will return null instead of throwing exception if
 * {@link #next()} is called at end of iteration.
 * <p>
 * @since 0.08
 * @author Christopher Barber
 */
public class SingleIterator<E> extends UnmodifiableIterator<E>
{
	/*-------
	 * State
	 */
	
	private @Nullable E _value;

	/*--------------
	 * Construction
	 */
	
	public SingleIterator(E value)
	{
		_value = value;
	}
	
	/*------------------
	 * Iterator methods
	 */
	
	@Override
	public boolean hasNext()
	{
		return _value != null;
	}

	/**
	 * Returns the next element in the iterator or null.
	 */
	@Override
	public @Nullable E next()
	{
		final E val = _value;
		_value = null;
		return val;
	}
}
