Java example source code file (Test7190310.java)

This example Java source code file (Test7190310.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

interruptedexception, object, referencequeue, string, test7190310, the, thread, throwable, weakreference

The Test7190310.java Java example source code

/*
 * Copyright (c) 2012, 2013, 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 7190310
 * @summary Inlining WeakReference.get(), and hoisting $referent may lead to non-terminating loops
 * @run main/othervm/timeout=600 -Xbatch Test7190310
 */

/*
 * Note bug exhibits as infinite loop, timeout is helpful.
 * It should normally finish pretty quickly, but on some especially slow machines
 * it may not.  The companion _unsafe test lacks a timeout, but that is okay.
 */

import java.lang.ref.*;

public class Test7190310 {
  private static Object str = new Object() {
    public String toString() {
      return "The Object";
    }

    protected void finalize() throws Throwable {
      System.out.println("The Object is being finalized");
      super.finalize();
    }
  };
  private final static ReferenceQueue<Object> rq =
      new ReferenceQueue<Object>();
  private final static WeakReference<Object> wr =
      new WeakReference<Object>(str, rq);

  public static void main(String[] args)
      throws InterruptedException {
    Thread reader = new Thread() {
      public void run() {
        while (wr.get() != null) {
        }
        System.out.println("wr.get() returned null");
      }
    };

    Thread queueReader = new Thread() {
      public void run() {
        try {
          Reference<? extends Object> ref = rq.remove();
          System.out.println(ref);
          System.out.println("queueReader returned, ref==wr is "
              + (ref == wr));
        } catch (InterruptedException e) {
          System.err.println("Sleep interrupted - exiting");
        }
      }
    };

    reader.start();
    queueReader.start();

    Thread.sleep(1000);
    str = null;
    System.gc();
  }
}