001    /*
002     * Copyright (C) 2009 Google Inc.
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    
017    package com.google.common.util.concurrent;
018    
019    import com.google.common.annotations.Beta;
020    
021    import javax.annotation.Nullable;
022    
023    /**
024     * A simple ListenableFuture that holds a value or an exception.
025     *
026     * @author Sven Mawson
027     * @since 1
028     */
029    @Beta
030    public class ValueFuture<V> extends AbstractListenableFuture<V> {
031    
032      /**
033       * Creates a new {@code ValueFuture} in the default state.
034       */
035      public static <T> ValueFuture<T> create() {
036        return new ValueFuture<T>();
037      }
038    
039      /**
040       * Explicit private constructor, use the {@link #create} factory method to
041       * create instances of {@code ValueFuture}.
042       */
043      private ValueFuture() {}
044    
045      /**
046       * Sets the value of this future.  This method will return {@code true} if
047       * the value was successfully set, or {@code false} if the future has already
048       * been set or cancelled.
049       *
050       * @param newValue the value the future should hold.
051       * @return true if the value was successfully set.
052       */
053      @Override
054      public boolean set(@Nullable V newValue) {
055        return super.set(newValue);
056      }
057    
058      /**
059       * Sets the future to having failed with the given exception.  This exception
060       * will be wrapped in an ExecutionException and thrown from the get methods.
061       * This method will return {@code true} if the exception was successfully set,
062       * or {@code false} if the future has already been set or cancelled.
063       *
064       * @param t the exception the future should hold.
065       * @return true if the exception was successfully set.
066       */
067      @Override
068      public boolean setException(Throwable t) {
069        return super.setException(t);
070      }
071    
072      /**
073       * {@inheritDoc}
074       *
075       * <p>A ValueFuture is never considered in the running state, so the
076       * {@code mayInterruptIfRunning} argument is ignored.
077       */
078      @Override
079      public boolean cancel(boolean mayInterruptIfRunning) {
080        return super.cancel();
081      }
082    }