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Java 1.6+ Library with tons of utility classes required in all projects
There is a newer version: 9.5.5
/**
 * Copyright (C) 2014-2016 Philip Helger (www.helger.com)
 * philip[at]helger[dot]com
 *
 * Licensed 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 com.helger.commons.callback.adapter;

import javax.annotation.Nonnull;
import javax.annotation.Nullable;
import javax.annotation.concurrent.Immutable;

import com.helger.commons.ValueEnforcer;
import com.helger.commons.callback.IThrowingCallable;
import com.helger.commons.callback.IThrowingRunnable;
import com.helger.commons.string.ToStringGenerator;

/**
 * A helper class that converts a {@link IThrowingRunnable} into an
 * {@link IThrowingCallable}.
 *
 * @author Philip Helger
 * @param 
 *        The callable result type.
 * @param 
 *        Exception type to be thrown
 */
@Immutable
public class AdapterThrowingRunnableToCallable 
                                               implements IThrowingCallable 
{
  private final IThrowingRunnable  m_aRunnable;
  private final DATATYPE m_aResult;

  public AdapterThrowingRunnableToCallable (@Nonnull final IThrowingRunnable  aRunnable)
  {
    this (aRunnable, null);
  }

  public AdapterThrowingRunnableToCallable (@Nonnull final IThrowingRunnable  aRunnable,
                                            @Nullable final DATATYPE aResult)
  {
    m_aRunnable = ValueEnforcer.notNull (aRunnable, "Runnable");
    m_aResult = aResult;
  }

  @Nonnull
  public IThrowingRunnable  getRunnable ()
  {
    return m_aRunnable;
  }

  @Nullable
  public DATATYPE getResult ()
  {
    return m_aResult;
  }

  @Nullable
  public DATATYPE call () throws EXTYPE
  {
    m_aRunnable.run ();
    return m_aResult;
  }

  @Override
  public String toString ()
  {
    return new ToStringGenerator (this).append ("runnable", m_aRunnable).append ("result", m_aResult).toString ();
  }

  /**
   * Create a callable that always returns null.
   *
   * @param aRunnable
   *        The runnable to be executed.
   * @return The created {@link AdapterThrowingRunnableToCallable} object.
   * @param 
   *        Exception type to be thrown
   */
  @Nonnull
  public static  AdapterThrowingRunnableToCallable  createAdapter (@Nonnull final IThrowingRunnable  aRunnable)
  {
    return new AdapterThrowingRunnableToCallable <> (aRunnable);
  }

  /**
   * Create a callable that always returns the passed value.
   *
   * @param aRunnable
   *        The runnable to be executed.
   * @param aResult
   *        The expected result from calling {@link IThrowingCallable#call()} .
   *        May be null.
   * @return The created {@link AdapterThrowingRunnableToCallable} object.
   * @param 
   *        The callable result type.
   * @param 
   *        Exception type to be thrown
   */
  @Nonnull
  public static  AdapterThrowingRunnableToCallable  createAdapter (@Nonnull final IThrowingRunnable  aRunnable,
                                                                                                                         @Nullable final DATATYPE aResult)
  {
    return new AdapterThrowingRunnableToCallable <> (aRunnable, aResult);
  }
}