/*******************************************************************************
* Copyright (c) 2002 - 2006 IBM Corporation.
* All rights reserved. This program and the accompanying materials
* are made available under the terms of the Eclipse Public License v1.0
* which accompanies this distribution, and is available at
* http://www.eclipse.org/legal/epl-v10.html
*
* Contributors:
* IBM Corporation - initial API and implementation
*******************************************************************************/
package com.ibm.wala.util.collections;
import java.util.Iterator;
import java.util.NoSuchElementException;
/**
* A singleton iterator for an object which is guaranteed to be not-null. Exploiting this invariant
* allows this class to be slightly more efficient than Collections.iterator()
*/
public class NonNullSingletonIterator<T> implements Iterator<T> {
private T it;
/**
* @param o the single object in this collection, must be non-null
*/
public NonNullSingletonIterator(T o) {
if (o == null) {
throw new IllegalArgumentException("o is null");
}
this.it = o;
}
@Override
public boolean hasNext() {
return it != null;
}
@Override
public T next() {
if (it == null) {
throw new NoSuchElementException();
} else {
T result = it;
it = null;
return result;
}
}
@Override
public void remove() throws UnsupportedOperationException {
throw new UnsupportedOperationException();
}
public static <T> NonNullSingletonIterator<T> make(T item) {
return new NonNullSingletonIterator<T>(item);
}
}