/*******************************************************************************
* Copyright (c) 2007, 2015 IBM Corporation and others.
* 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 org.eclipse.core.internal.databinding;
/**
* Created to avoid a dependency on java.util.LinkedList, see bug 205224.
*
* @since 1.1
*
*/
public class Queue {
static class Entry {
Object object;
Entry(Object o) {
this.object = o;
}
Entry next;
}
Entry first;
Entry last;
/**
* Adds the given object to the end of the queue.
*
* @param o
*/
public void enqueue(Object o) {
Entry oldLast = last;
last = new Entry(o);
if (oldLast != null) {
oldLast.next = last;
} else {
first = last;
}
}
/**
* Returns the first object in the queue. The queue must not be empty.
*
* @return the first object
*/
public Object dequeue() {
Entry oldFirst = first;
if (oldFirst == null) {
throw new IllegalStateException();
}
first = oldFirst.next;
if (first == null) {
last = null;
}
oldFirst.next = null;
return oldFirst.object;
}
/**
* Returns <code>true</code> if the list is empty.
*
* @return <code>true</code> if the list is empty
*/
public boolean isEmpty() {
return first == null;
}
}