| /* |
| * Licensed to the Apache Software Foundation (ASF) under one or more |
| * contributor license agreements. See the NOTICE file distributed with |
| * this work for additional information regarding copyright ownership. |
| * The ASF licenses this file to You 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 org.apache.tomcat.util.collections; |
| |
| import java.util.Vector; |
| |
| /** |
| * A simple FIFO queue class which causes the calling thread to wait |
| * if the queue is empty and notifies threads that are waiting when it |
| * is not empty. |
| * |
| * @author Anil V (akv@eng.sun.com) |
| */ |
| public class Queue { |
| private Vector vector = new Vector(); |
| private boolean stopWaiting=false; |
| private boolean waiting=false; |
| |
| /** |
| * Put the object into the queue. |
| * |
| * @param object the object to be appended to the |
| * queue. |
| */ |
| public synchronized void put(Object object) { |
| vector.addElement(object); |
| notify(); |
| } |
| |
| /** Break the pull(), allowing the calling thread to exit |
| */ |
| public synchronized void stop() { |
| stopWaiting=true; |
| // just a hack to stop waiting |
| if( waiting ) notify(); |
| } |
| |
| /** |
| * Pull the first object out of the queue. Wait if the queue is |
| * empty. |
| */ |
| public synchronized Object pull() { |
| while (isEmpty()) { |
| try { |
| waiting=true; |
| wait(); |
| } catch (InterruptedException ex) { |
| } |
| waiting=false; |
| if( stopWaiting ) return null; |
| } |
| return get(); |
| } |
| |
| /** |
| * Get the first object out of the queue. Return null if the queue |
| * is empty. |
| */ |
| public synchronized Object get() { |
| Object object = peek(); |
| if (object != null) |
| vector.removeElementAt(0); |
| return object; |
| } |
| |
| /** |
| * Peek to see if something is available. |
| */ |
| public Object peek() { |
| if (isEmpty()) |
| return null; |
| return vector.elementAt(0); |
| } |
| |
| /** |
| * Is the queue empty? |
| */ |
| public boolean isEmpty() { |
| return vector.isEmpty(); |
| } |
| |
| /** |
| * How many elements are there in this queue? |
| */ |
| public int size() { |
| return vector.size(); |
| } |
| } |