001/*
002 * ModeShape (http://www.modeshape.org)
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 */
016package org.modeshape.common.util;
017
018import java.util.concurrent.Future;
019import java.util.concurrent.TimeUnit;
020import org.modeshape.common.annotation.Immutable;
021
022/**
023 * A {@link Future} implementation that is immediately done.
024 * 
025 * @param <V> the type of result
026 */
027@Immutable
028public final class ImmediateFuture<V> implements Future<V> {
029
030    /**
031     * Factory method to more easily create an immediate future
032     * 
033     * @param <T> the value type
034     * @param value the value that the future should return
035     * @return the new future; never null
036     */
037    public static <T> ImmediateFuture<T> create( T value ) {
038        return new ImmediateFuture<T>(value);
039    }
040
041    private final V result;
042
043    /**
044     * Create a new {@link Future} instance that is completed immediately and returns the supplied result.
045     * 
046     * @param value the value that the future should return
047     */
048    public ImmediateFuture( V value ) {
049        this.result = value;
050    }
051
052    @Override
053    public boolean cancel( boolean mayInterruptIfRunning ) {
054        return false; // completed
055    }
056
057    @Override
058    public V get() {
059        return result;
060    }
061
062    @Override
063    public V get( long timeout,
064                  TimeUnit unit ) {
065        return result;
066    }
067
068    @Override
069    public boolean isCancelled() {
070        return false;
071    }
072
073    @Override
074    public boolean isDone() {
075        return true;
076    }
077
078}