001/*
002 * Copyright (C) 2009 The Guava Authors
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 * http://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016
017package com.google.common.util.concurrent;
018
019import com.google.common.annotations.Beta;
020
021import javax.annotation.Nullable;
022
023/**
024 * A {@link ListenableFuture} whose result may be set by a {@link #set(Object)}
025 * or {@link #setException(Throwable)} call.
026 *
027 * @author Sven Mawson
028 * @since 9 (in version 1 as {@code ValueFuture})
029 */
030@Beta
031public final class SettableFuture<V> extends AbstractListenableFuture<V> {
032
033  /**
034   * Creates a new {@code SettableFuture} in the default state.
035   */
036  public static <V> SettableFuture<V> create() {
037    return new SettableFuture<V>();
038  }
039
040  /**
041   * Explicit private constructor, use the {@link #create} factory method to
042   * create instances of {@code SettableFuture}.
043   */
044  private SettableFuture() {}
045
046  /**
047   * Sets the value of this future.  This method will return {@code true} if
048   * the value was successfully set, or {@code false} if the future has already
049   * been set or cancelled.
050   *
051   * @param newValue the value the future should hold.
052   * @return true if the value was successfully set.
053   */
054  @Override
055  public boolean set(@Nullable V newValue) {
056    return super.set(newValue);
057  }
058
059  /**
060   * Sets the future to having failed with the given exception.  This exception
061   * will be wrapped in an ExecutionException and thrown from the get methods.
062   * This method will return {@code true} if the exception was successfully set,
063   * or {@code false} if the future has already been set or cancelled.
064   *
065   * @param t the exception the future should hold.
066   * @return true if the exception was successfully set.
067   */
068  @Override
069  public boolean setException(Throwable t) {
070    return super.setException(t);
071  }
072
073  /**
074   * {@inheritDoc}
075   *
076   * <p>A SettableFuture is never considered in the running state, so the
077   * {@code mayInterruptIfRunning} argument is ignored.
078   */
079  @Override
080  public boolean cancel(boolean mayInterruptIfRunning) {
081    return super.cancel();
082  }
083}