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Java example source code file (CompletedFuture.java)

This example Java source code file (CompletedFuture.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

completedfuture, executionexception, ioexception, nullpointerexception, override, securityexception, threading, threads, throwable, timeunit

The CompletedFuture.java Java example source code

/*
 * Copyright (c) 2008, 2010, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

package sun.nio.ch;

import java.util.concurrent.Future;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.ExecutionException;
import java.io.IOException;

/**
 * A Future representing the result of an I/O operation that has already
 * completed.
 */

final class CompletedFuture<V> implements Future {
    private final V result;
    private final Throwable exc;

    private CompletedFuture(V result, Throwable exc) {
        this.result = result;
        this.exc = exc;
    }

    static <V> CompletedFuture withResult(V result) {
        return new CompletedFuture<V>(result, null);
    }

    static <V> CompletedFuture withFailure(Throwable exc) {
        // exception must be IOException or SecurityException
        if (!(exc instanceof IOException) && !(exc instanceof SecurityException))
            exc = new IOException(exc);
        return new CompletedFuture<V>(null, exc);
    }

    static <V> CompletedFuture withResult(V result, Throwable exc) {
        if (exc == null) {
            return withResult(result);
        } else {
            return withFailure(exc);
        }
    }

    @Override
    public V get() throws ExecutionException {
        if (exc != null)
            throw new ExecutionException(exc);
        return result;
    }

    @Override
    public V get(long timeout, TimeUnit unit) throws ExecutionException {
        if (unit == null)
            throw new NullPointerException();
        if (exc != null)
            throw new ExecutionException(exc);
        return result;
    }

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

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

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

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