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Java example source code file (UncheckedThrowingFuture.java)

This example Java source code file (UncheckedThrowingFuture.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

assertionerror, executor, gwtcompatible, listenablefuture, override, runtimeexception, threading, threads, timeunit, uncheckedthrowingfuture, unreachable

The UncheckedThrowingFuture.java Java example source code

/*
 * Copyright (C) 2011 The Guava Authors
 *
 * 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.google.common.util.concurrent;

import static com.google.common.base.Preconditions.checkNotNull;

import com.google.common.annotations.GwtCompatible;

import java.util.concurrent.Executor;
import java.util.concurrent.Future;
import java.util.concurrent.TimeUnit;

/**
 * A {@link Future} implementation which always throws directly from calls to {@code get()} (i.e.
 * not wrapped in {@code ExecutionException}. For just a normal failure, use {@link
 * SettableFuture}).
 *
 * <p>Useful for testing the behavior of Future utilities against odd futures.
 *
 * @author Anthony Zana
 */
@GwtCompatible
final class UncheckedThrowingFuture<V> implements ListenableFuture {
  private final Error error;
  private final RuntimeException runtime;

  public static <V> ListenableFuture throwingError(Error error) {
    return new UncheckedThrowingFuture<V>(error);
  }

  public static <V> ListenableFuture throwingRuntimeException(RuntimeException e) {
    return new UncheckedThrowingFuture<V>(e);
  }

  private UncheckedThrowingFuture(Error error) {
    this.error = checkNotNull(error);
    this.runtime = null;
  }

  public UncheckedThrowingFuture(RuntimeException e) {
    this.runtime = checkNotNull(e);
    this.error = null;
  }

  @Override
  public boolean cancel(boolean mayInterruptIfRunning) {
    return false;
  }

  @Override
  public boolean isCancelled() {
    return false;
  }

  @Override
  public boolean isDone() {
    return true;
  }

  @Override
  public V get() {
    throwOnGet();
    throw new AssertionError("Unreachable");
  }

  @Override
  public V get(long timeout, TimeUnit unit) {
    checkNotNull(unit);
    throwOnGet();
    throw new AssertionError();
  }

  @Override
  public void addListener(Runnable listener, Executor executor) {
    checkNotNull(listener);
    // TODO(cpovirk): Catch RuntimeExceptions
    executor.execute(listener);
  }

  private void throwOnGet() {
    if (error != null) {
      throw error;
    } else {
      throw runtime;
    }
  }
}

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