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/***********************************************************************************************************************
 *
 * Copyright (C) 2010-2013 by the Stratosphere project (http://stratosphere.eu)
 *
 * 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 eu.stratosphere.pact.runtime.util;

import java.util.Iterator;
import java.util.NoSuchElementException;

/**
 * An {@link Iterator} that contains only a single element. The element can be reset such that the iterator can be used
 * multiple times. Initially, the iterator is empty until an element is set via {@link #set(Object)}.
 * 
 * @param The generic type of the iterator.
 */
public final class SingleElementIterator implements Iterator {
		
		private E current;
		private boolean available = false;
		
		/**
		 * Resets the element. After this call, the iterator has one element available, which is the given element.
		 * 
		 * @param current The element to make available to the iterator.
		 */
		public void set(E current) {
			this.current = current;
			this.available = true;
		}

		@Override
		public boolean hasNext() {
			return available;
		}

		@Override
		public E next() {
			if (available) {
				available = false;
				return current;
			} else {
				throw new NoSuchElementException();
			}
		}

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