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.lib.util.Check;
022
023import java.util.concurrent.Callable;
024
025/**
026 * Adapter class that allows <code>Runnable</code>s and <code>Callable</code>s to
027 * be treated as the other.
028 */
029public class RunnableCallable implements Callable<Void>, Runnable {
030  private Runnable runnable;
031  private Callable<?> callable;
032
033  /**
034   * Constructor that takes a runnable.
035   *
036   * @param runnable runnable.
037   */
038  public RunnableCallable(Runnable runnable) {
039    this.runnable = Check.notNull(runnable, "runnable");
040  }
041
042  /**
043   * Constructor that takes a callable.
044   *
045   * @param callable callable.
046   */
047  public RunnableCallable(Callable<?> callable) {
048    this.callable = Check.notNull(callable, "callable");
049  }
050
051  /**
052   * Invokes the wrapped callable/runnable as a callable.
053   *
054   * @return void
055   *
056   * @throws Exception thrown by the wrapped callable/runnable invocation.
057   */
058  @Override
059  public Void call() throws Exception {
060    if (runnable != null) {
061      runnable.run();
062    } else {
063      callable.call();
064    }
065    return null;
066  }
067
068  /**
069   * Invokes the wrapped callable/runnable as a runnable.
070   *
071   * @throws RuntimeException thrown by the wrapped callable/runnable invocation.
072   */
073  @Override
074  public void run() {
075    if (runnable != null) {
076      runnable.run();
077    } else {
078      try {
079        callable.call();
080      } catch (Exception ex) {
081        throw new RuntimeException(ex);
082      }
083    }
084  }
085
086  /**
087   * Returns the class name of the wrapper callable/runnable.
088   *
089   * @return the class name of the wrapper callable/runnable.
090   */
091  public String toString() {
092    return (runnable != null) ? runnable.getClass().getSimpleName() : callable.getClass().getSimpleName();
093  }
094}