/***********************************************************************************************************************
* 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 empty iterator that never returns anything.
*/
public final class EmptyIterator<E> implements Iterator<E> {
/**
* The singleton instance.
*/
private static final EmptyIterator<Object> INSTANCE = new EmptyIterator<Object>();
/**
* Gets a singleton instance of the empty iterator.
*
* @param <E> The type of the objects (not) returned by the iterator.
* @return An instance of the iterator.
*/
public static <E> Iterator<E> get() {
@SuppressWarnings("unchecked")
Iterator<E> iter = (Iterator<E>) INSTANCE;
return iter;
}
/**
* Always returns false, since this iterator is empty.
*
* @see java.util.Iterator#hasNext()
*/
@Override
public boolean hasNext() {
return false;
}
/**
* Always throws a {@link java.util.NoSuchElementException}.
*
* @see java.util.Iterator#next()
*/
@Override
public E next() {
throw new NoSuchElementException();
}
/**
* Throws a {@link java.lang.UnsupportedOperationException}.
*
* @see java.util.Iterator#remove()
*/
@Override
public void remove() {
throw new UnsupportedOperationException();
}
}