1 /* 2 * Copyright (C) 2009 Google Inc. 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 package com.google.common.util.concurrent; 18 19 /** 20 * A simple ListenableFuture that holds a value or an exception. 21 * 22 * @author Sven Mawson 23 * @since 2009.09.15 <b>tentative</b> 24 */ 25 public class ValueFuture<V> extends AbstractListenableFuture<V> { 26 27 /** 28 * Creates a new {@code ValueFuture} in the default state. 29 */ create()30 public static <T> ValueFuture<T> create() { 31 return new ValueFuture<T>(); 32 } 33 34 /** 35 * Explicit private constructor, use the {@link #create} factory method to 36 * create instances of {@code ValueFuture}. 37 */ ValueFuture()38 private ValueFuture() {} 39 40 /** 41 * Sets the value of this future. This method will return {@code true} if 42 * the value was successfully set, or {@code false} if the future has already 43 * been set or cancelled. 44 * 45 * @param newValue the value the future should hold. 46 * @return true if the value was successfully set. 47 */ 48 @Override set(V newValue)49 public boolean set(V newValue) { 50 return super.set(newValue); 51 } 52 53 /** 54 * Sets the future to having failed with the given exception. This exception 55 * will be wrapped in an ExecutionException and thrown from the get methods. 56 * This method will return {@code true} if the exception was successfully set, 57 * or {@code false} if the future has already been set or cancelled. 58 * 59 * @param t the exception the future should hold. 60 * @return true if the exception was successfully set. 61 */ 62 @Override setException(Throwable t)63 public boolean setException(Throwable t) { 64 return super.setException(t); 65 } 66 67 /** 68 * {@inheritDoc} 69 * 70 * <p>A ValueFuture is never considered in the running state, so the 71 * {@code mayInterruptIfRunning} argument is ignored. 72 */ 73 @Override cancel(boolean mayInterruptIfRunning)74 public boolean cancel(boolean mayInterruptIfRunning) { 75 return super.cancel(); 76 } 77 } 78