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/*******************************************************************************
* Copyright (c) 2005, 2009 Oracle. 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:
* Oracle - initial API and implementation
******************************************************************************/
package org.eclipse.jpt.utility.internal.iterators;
import java.util.ListIterator;
import java.util.NoSuchElementException;
import org.eclipse.jpt.utility.internal.StringTools;
/**
* A <code>SingleElementListIterator</code> holds a single element
* and returns it with the first call to {@link next()}, at
* which point it will return <code>false</code> to any subsequent
* call to {@link #hasNext()}. Likewise, it will return <code>false</code>
* to a call to {@link #hasPrevious()} until a call to {@link #next()},
* at which point a call to {@link #previous()} will return the
* single element.
* <p>
* A <code>SingleElementListIterator</code> is equivalent to the
* {@link Iterator} returned by:
* {@link java.util.Collections#singletonList(element)}<code>.listIterator()</code>
*
* @param <E> the type of elements returned by the iterator
*
* @see org.eclipse.jpt.utility.internal.iterables.SingleElementListIterable
*/
public class SingleElementListIterator<E>
implements ListIterator<E>
{
private final E element;
private boolean hasNext;
/**
* Construct a list iterator that returns only the specified element.
*/
public SingleElementListIterator(E element) {
super();
this.element = element;
this.hasNext = true;
}
public boolean hasNext() {
return this.hasNext;
}
public E next() {
if (this.hasNext) {
this.hasNext = false;
return this.element;
}
throw new NoSuchElementException();
}
public int nextIndex() {
return this.hasNext ? 0 : 1;
}
public boolean hasPrevious() {
return ! this.hasNext;
}
public E previous() {
if (this.hasNext) {
throw new NoSuchElementException();
}
this.hasNext = true;
return this.element;
}
public int previousIndex() {
return this.hasNext ? -1 : 0;
}
public void add(E e) {
throw new UnsupportedOperationException();
}
public void set(E e) {
throw new UnsupportedOperationException();
}
public void remove() {
throw new UnsupportedOperationException();
}
@Override
public String toString() {
return StringTools.buildToStringFor(this, this.element);
}
}
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