org.apache.river.norm.Queue Maven / Gradle / Ivy
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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.river.norm;
import java.util.Collections;
import java.util.LinkedList;
import java.util.List;
/**
* Simple thread-safe FIFO sequence.
*
* @author Sun Microsystems, Inc.
*/
class Queue {
/** List we actually store stuff in */
final private List lst = Collections.synchronizedList(new LinkedList());
/**
* Enqueue an item.
*/
synchronized void enqueue(Object o) {
lst.add(o);
notifyAll();
}
/**
* Block until the queue is non-empty and return the first item.
*
* @throws InterruptedException if the current thread is interrupted
* while the queue is waiting for an item to appear
*/
synchronized Object dequeue() throws InterruptedException {
while (lst.isEmpty()) {
wait();
}
return lst.remove(0);
}
}