/*******************************************************************************
* Copyright (c) 1998, 2015 Oracle and/or its affiliates. All rights reserved.
* This program and the accompanying materials are made available under the
* terms of the Eclipse Public License v1.0 and Eclipse Distribution License v. 1.0
* which accompanies this distribution.
* The Eclipse Public License is available at http://www.eclipse.org/legal/epl-v10.html
* and the Eclipse Distribution License is available at
* http://www.eclipse.org/org/documents/edl-v10.php.
*
* Contributors:
* Oracle - initial API and implementation from Oracle TopLink
******************************************************************************/
package org.eclipse.persistence.tools.workbench.utility.iterators;
import java.util.ListIterator;
import java.util.NoSuchElementException;
import org.eclipse.persistence.tools.workbench.utility.ClassTools;
/**
* A <code>SingleElementListIterator</code> holds a single element
* and returns it with the first call to <code>next()</code>, at
* which point it will return <code>false</code> to any subsequent
* call to <code>hasNext()</code>. Likewise, it will return <code>false</code>
* to a call to <code>hasPrevious()</code> until a call to <code>next()</code>,
* at which point a call to <code>previous()</code> will return the
* single element.
* <p>
* A <code>SingleElementIterator</code> is equivalent to the
* <code>Iterator</code> returned by:
* <code>java.util.Collections.singletonList(element).listIterator()</code>
*/
public class SingleElementListIterator implements ListIterator {
private Object element;
private Object next;
private static final Object END = new Object();
/**
* Construct a list iterator that returns only the specified element.
*/
public SingleElementListIterator(Object element) {
super();
this.element = element;
this.next = element;
}
/**
* @see java.util.ListIterator#hasNext()
*/
public boolean hasNext() {
return this.next == this.element;
}
/**
* @see java.util.ListIterator#next()
*/
public Object next() {
if (this.next == END) {
throw new NoSuchElementException();
}
this.next = END;
return this.element;
}
/**
* @see java.util.ListIterator#nextIndex()
*/
public int nextIndex() {
return (this.next == this.element) ? 0 : 1;
}
/**
* @see java.util.ListIterator#hasPrevious()
*/
public boolean hasPrevious() {
return this.next == END;
}
/**
* @see java.util.ListIterator#previous()
*/
public Object previous() {
if (this.next == this.element) {
throw new NoSuchElementException();
}
this.next = this.element;
return this.element;
}
/**
* @see java.util.ListIterator#nextIndex()
*/
public int previousIndex() {
return (this.next == END) ? 0 : -1;
}
/**
* @see java.util.ListIterator#add(Object)
*/
public void add(Object o) {
throw new UnsupportedOperationException();
}
/**
* @see java.util.ListIterator#set(Object)
*/
public void set(Object o) {
throw new UnsupportedOperationException();
}
/**
* @see java.util.ListIterator#remove()
*/
public void remove() {
throw new UnsupportedOperationException();
}
/**
* @see Object#toString()
*/
public String toString() {
return ClassTools.shortClassNameForObject(this) + '(' + this.element + ')';
}
}