Quelle ReferenceEnqueue.java Sprache: JAVA

/*
* Copyright (c) 2011, 2020, 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.
*
* 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.
*/

/* @test
* @bug 4268317 8132306 8175797
* @summary Test if Reference.enqueue() works properly with GC
* @run main ReferenceEnqueue
*/

import java.lang.ref.*;
import java.util.ArrayList;
import java.util.List;

public class ReferenceEnqueue {

    public static void main(String args[]) throws Exception {
        for (int i=0; i < 5; i++) {
            new WeakRef().run();
            new ExplicitEnqueue().run();
        }
        System.out.println("Test passed.");
    }

    static class WeakRef {
        final ReferenceQueue<Object> queue = new ReferenceQueue<Object>();
        final Reference<Object> ref;
        final int iterations = 1000;

        WeakRef() {
            this.ref = new WeakReference<Object>(new Object(), queue);
        }

        void run() throws InterruptedException {
            boolean enqueued = false;
            System.gc();
            for (int i = 0; i < iterations; i++) {
                System.gc();
                enqueued = (queue.remove(100) == ref);
                if (enqueued) break;
            }

            if (!enqueued) {
                // GC have not enqueued refWeak for the timeout period
                throw new RuntimeException("Error: reference not enqueued");
            }

            if (ref.enqueue() == true) {
                // enqueue() should return false since
                // ref is already enqueued by the GC
                throw new RuntimeException("Error: enqueue() returned true;"
                        + " expected false");
            }
        }
    }

    static class ExplicitEnqueue {
        final ReferenceQueue<Object> queue = new ReferenceQueue<>();
        final List<Reference<Object>> refs = new ArrayList<>();
        final int iterations = 1000;

        ExplicitEnqueue() {
            this.refs.add(new SoftReference<>(new Object(), queue));
            this.refs.add(new WeakReference<>(new Object(), queue));
            this.refs.add(new PhantomReference<>(new Object(), queue));
        }

        void run() throws InterruptedException {
            for (Reference<Object> ref : refs) {
                if (ref.enqueue() == false) {
                    throw new RuntimeException("Error: enqueue failed");
                }
                if (!ref.refersTo(null)) {
                    throw new RuntimeException("Error: referent must be cleared");
                }
            }

            System.gc();
            for (int i = 0; refs.size() > 0 && i < iterations; i++) {
                Reference<Object> ref = (Reference<Object>)queue.poll();
                if (ref == null) {
                    System.gc();
                    Thread.sleep(100);
                    continue;
                }

                if (refs.remove(ref) == false) {
                    throw new RuntimeException("Error: unknown reference " + ref);
                }
            }

            if (!refs.isEmpty()) {
                throw new RuntimeException("Error: not all references are removed");
            }
        }
    }
}

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