ClearHandleTable.java

/*
 * Copyright (c) 2000, 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.
 *
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 * questions.
 */

/* @test
 * @bug 4332184
 * @summary Ensure that ObjectOutputStream properly releases strong references
 *          to written objects when reset() is called.
 */

import java.io.*;
import java.lang.ref.WeakReference;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

public class ClearHandleTable {
    private static final int TIMES = 1000;

    public static void main(String[] args) throws Exception {
        final int nreps = 100;
        ObjectOutputStream oout =
            new ObjectOutputStream(new ByteArrayOutputStream());
        List<WeakReference<?>> refs = new ArrayList<>(nreps);

        for (int i = 0; i < nreps; i++) {
            String str = new String("blargh");
            oout.writeObject(str);
            refs.add(new WeakReference<Object>(str));
        }

        oout.reset();

        int count = 0;
        for (int i=0; i<TIMES; i++) {
            // relying on, possibly multiple, System.gc calls to clear weak references
            System.gc();

            Iterator<WeakReference<?>> itr = refs.iterator();
            while(itr.hasNext()) {
                WeakReference<?> ref = itr.next();
                if (ref.get() == null) {
                    itr.remove();
                }
            }
            if (refs.isEmpty())
                break;
            Thread.sleep(20);
            count++;
            if (count % 10 == 0)
                System.out.println("Looping " + count + " times");
        }

        if (!refs.isEmpty()) {
            throw new Error("failed to garbage collect object");
        }
    }
}