| /** |
| * 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.hadoop.util; |
| |
| import java.util.concurrent.locks.Condition; |
| |
| /** |
| * Represents an object that you can wait for. |
| */ |
| public class Waitable<T> { |
| private T val; |
| private final Condition cond; |
| |
| public Waitable(Condition cond) { |
| this.val = null; |
| this.cond = cond; |
| } |
| |
| public T await() throws InterruptedException { |
| while (this.val == null) { |
| this.cond.await(); |
| } |
| return this.val; |
| } |
| |
| public void provide(T val) { |
| this.val = val; |
| this.cond.signalAll(); |
| } |
| |
| public boolean hasVal() { |
| return this.val != null; |
| } |
| |
| public T getVal() { |
| return this.val; |
| } |
| } |