001/**
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements.  See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership.  The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License.  You may obtain a copy of the License at
009 *
010 *     http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing, software
013 * distributed under the License is distributed on an "AS IS" BASIS,
014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015 * See the License for the specific language governing permissions and
016 * limitations under the License.
017 */
018
019package org.apache.hadoop.lib.lang;
020
021import org.apache.hadoop.classification.InterfaceAudience;
022import org.apache.hadoop.lib.util.Check;
023
024import java.util.concurrent.Callable;
025
026/**
027 * Adapter class that allows <code>Runnable</code>s and <code>Callable</code>s to
028 * be treated as the other.
029 */
030@InterfaceAudience.Private
031public class RunnableCallable implements Callable<Void>, Runnable {
032  private Runnable runnable;
033  private Callable<?> callable;
034
035  /**
036   * Constructor that takes a runnable.
037   *
038   * @param runnable runnable.
039   */
040  public RunnableCallable(Runnable runnable) {
041    this.runnable = Check.notNull(runnable, "runnable");
042  }
043
044  /**
045   * Constructor that takes a callable.
046   *
047   * @param callable callable.
048   */
049  public RunnableCallable(Callable<?> callable) {
050    this.callable = Check.notNull(callable, "callable");
051  }
052
053  /**
054   * Invokes the wrapped callable/runnable as a callable.
055   *
056   * @return void
057   *
058   * @throws Exception thrown by the wrapped callable/runnable invocation.
059   */
060  @Override
061  public Void call() throws Exception {
062    if (runnable != null) {
063      runnable.run();
064    } else {
065      callable.call();
066    }
067    return null;
068  }
069
070  /**
071   * Invokes the wrapped callable/runnable as a runnable.
072   *
073   * @throws RuntimeException thrown by the wrapped callable/runnable invocation.
074   */
075  @Override
076  public void run() {
077    if (runnable != null) {
078      runnable.run();
079    } else {
080      try {
081        callable.call();
082      } catch (Exception ex) {
083        throw new RuntimeException(ex);
084      }
085    }
086  }
087
088  /**
089   * Returns the class name of the wrapper callable/runnable.
090   *
091   * @return the class name of the wrapper callable/runnable.
092   */
093  @Override
094  public String toString() {
095    return (runnable != null) ? runnable.getClass().getSimpleName() : callable.getClass().getSimpleName();
096  }
097}