1 /*
   2  * Copyright (c) 2004, 2015, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  */
  23 
  24 /*
  25  * @test
  26  * @bug 5047639
  27  * @summary Check that the "java-level" APIs provide a consistent view of
  28  *          the thread list
  29  * @modules java.management
  30  */
  31 import java.lang.management.ManagementFactory;
  32 import java.lang.management.ThreadMXBean;
  33 import java.util.Map;
  34 
  35 public class ThreadLists {
  36     public static void main(String args[]) {
  37 
  38         // get top-level thread group
  39         ThreadGroup top = Thread.currentThread().getThreadGroup();
  40         ThreadGroup parent;
  41         do {
  42             parent = top.getParent();
  43             if (parent != null) top = parent;
  44         } while (parent != null);
  45 
  46         // get the thread count
  47         int activeCount = top.activeCount();
  48 
  49         Map<Thread, StackTraceElement[]> stackTraces = Thread.getAllStackTraces();
  50 
  51         ThreadMXBean threadBean = ManagementFactory.getThreadMXBean();
  52         int threadCount = threadBean.getThreadCount();
  53         long[] threadIds = threadBean.getAllThreadIds();
  54 
  55         System.out.println("ThreadGroup: " + activeCount + " active thread(s)");
  56         System.out.println("Thread: " + stackTraces.size() + " stack trace(s) returned");
  57         System.out.println("ThreadMXBean: " + threadCount + " live threads(s)");
  58         System.out.println("ThreadMXBean: " + threadIds.length + " thread Id(s)");
  59 
  60         // check results are consistent
  61         boolean failed = false;
  62         if (activeCount != stackTraces.size()) failed = true;
  63         if (activeCount != threadCount) failed = true;
  64         if (activeCount != threadIds.length) failed = true;
  65 
  66         if (failed) {
  67             throw new RuntimeException("inconsistent results");
  68         }
  69     }
  70 }