RunnableCallable.java

/*
 * Copyright (c) 2011, Cloudera, Inc. All Rights Reserved.
 *
 * Cloudera, Inc. 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
 *
 * This software 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 com.cloudera.lib.lang;

import com.cloudera.lib.util.Check;

import java.util.concurrent.Callable;

/**
 * Adapter class that allows <code>Runnable</code>s and <code>Callable</code>s to
 * be treated as the other.
 */
public class RunnableCallable implements Callable<Void>, Runnable {
  private Runnable runnable;
  private Callable<?> callable;

  /**
   * Constructor that takes a runnable.
   *
   * @param runnable runnable.
   */
  public RunnableCallable(Runnable runnable) {
    this.runnable = Check.notNull(runnable, "runnable");
  }

  /**
   * Constructor that takes a callable.
   * @param callable callable.
   */
  public RunnableCallable(Callable<?> callable) {
    this.callable = Check.notNull(callable, "callable");
  }

  /**
   * Invokes the wrapped callable/runnable as a callable.
   * @return void
   * @throws Exception thrown by the wrapped callable/runnable invocation.
   */
  @Override
  public Void call() throws Exception {
    if (runnable != null) {
      runnable.run();
    }
    else {
      callable.call();
    }
    return null;
  }

  /**
   * Invokes the wrapped callable/runnable as a runnable.
   * @return void
   * @throws Exception thrown by the wrapped callable/runnable invocation.
   */
  @Override
  public void run() {
    if (runnable != null) {
      runnable.run();
    }
    else {
      try {
        callable.call();
      }
      catch (Exception ex) {
        throw new RuntimeException(ex);
      }
    }
  }

  /**
   * Returns the class name of the wrapper callable/runnable.
   *
   * @return  the class name of the wrapper callable/runnable.
   */
  public String toString() {
    return (runnable != null) ? runnable.getClass().getSimpleName() : callable.getClass().getSimpleName();
  }
}