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/*
* 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.catalina.util;
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();
/**
* 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();
}
/**
* Pull the first object out of the queue. Wait if the queue is
* empty.
*/
public synchronized Object pull() {
while (isEmpty())
try {
wait();
} catch (InterruptedException ex) {
}
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();
}
}
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