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    
019    package org.apache.hadoop.lib.lang;
020    
021    import org.apache.hadoop.classification.InterfaceAudience;
022    import org.apache.hadoop.lib.util.Check;
023    
024    import 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
031    public 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      public String toString() {
094        return (runnable != null) ? runnable.getClass().getSimpleName() : callable.getClass().getSimpleName();
095      }
096    }