src/java.base/share/classes/sun/nio/ch/CompletedFuture.java

/*
 * Copyright (c) 2008, 2024, 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
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 */

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<V> {
    private final V result;
    private final Throwable exc;

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

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

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

    static <V> CompletedFuture<V> 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;
    }
}