Java example source code file (ImmediateFuture.java)

This example Java source code file (ImmediateFuture.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

annotation, executionexception, executor, immediatefailedcheckedfuture, immediatefuture, immediatesuccessfulcheckedfuture, immediatesuccessfulfuture, log, logging, nullable, override, runtimeexception, threading, threads, timeunit, todo, trustedfuture

The ImmediateFuture.java Java example source code

/*
 * Copyright (C) 2006 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 com.google.common.annotations.GwtIncompatible;
import com.google.common.util.concurrent.AbstractFuture.TrustedFuture;

import java.util.concurrent.ExecutionException;
import java.util.concurrent.Executor;
import java.util.concurrent.TimeUnit;
import java.util.logging.Level;
import java.util.logging.Logger;

import javax.annotation.Nullable;

/**
 * Implementations of {@code Futures.immediate*}.
 */
@GwtCompatible(emulated = true)
abstract class ImmediateFuture<V> implements ListenableFuture {
  private static final Logger log = Logger.getLogger(ImmediateFuture.class.getName());

  @Override
  public void addListener(Runnable listener, Executor executor) {
    checkNotNull(listener, "Runnable was null.");
    checkNotNull(executor, "Executor was null.");
    try {
      executor.execute(listener);
    } catch (RuntimeException e) {
      // ListenableFuture's contract is that it will not throw unchecked exceptions, so log the bad
      // runnable and/or executor and swallow it.
      log.log(
          Level.SEVERE,
          "RuntimeException while executing runnable " + listener + " with executor " + executor,
          e);
    }
  }

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

  @Override
  public abstract V get() throws ExecutionException;

  @Override
  public V get(long timeout, TimeUnit unit) throws ExecutionException {
    checkNotNull(unit);
    return get();
  }

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

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

  static class ImmediateSuccessfulFuture<V> extends ImmediateFuture {
    static final ImmediateSuccessfulFuture<Object> NULL =
        new ImmediateSuccessfulFuture<Object>(null);
    @Nullable private final V value;

    ImmediateSuccessfulFuture(@Nullable V value) {
      this.value = value;
    }

    // TODO(lukes): Consider throwing InterruptedException when appropriate.
    @Override
    public V get() {
      return value;
    }
  }

  @GwtIncompatible // TODO
  static class ImmediateSuccessfulCheckedFuture<V, X extends Exception> extends ImmediateFuture
      implements CheckedFuture<V, X> {
    @Nullable private final V value;

    ImmediateSuccessfulCheckedFuture(@Nullable V value) {
      this.value = value;
    }

    @Override
    public V get() {
      return value;
    }

    @Override
    public V checkedGet() {
      return value;
    }

    @Override
    public V checkedGet(long timeout, TimeUnit unit) {
      checkNotNull(unit);
      return value;
    }
  }

  static final class ImmediateFailedFuture<V> extends TrustedFuture {
    ImmediateFailedFuture(Throwable thrown) {
      setException(thrown);
    }
  }

  static final class ImmediateCancelledFuture<V> extends TrustedFuture {
    ImmediateCancelledFuture() {
      cancel(false);
    }
  }

  @GwtIncompatible // TODO
  static class ImmediateFailedCheckedFuture<V, X extends Exception> extends ImmediateFuture
      implements CheckedFuture<V, X> {
    private final X thrown;

    ImmediateFailedCheckedFuture(X thrown) {
      this.thrown = thrown;
    }

    @Override
    public V get() throws ExecutionException {
      throw new ExecutionException(thrown);
    }

    @Override
    public V checkedGet() throws X {
      throw thrown;
    }

    @Override
    public V checkedGet(long timeout, TimeUnit unit) throws X {
      checkNotNull(unit);
      throw thrown;
    }
  }
}