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  */
  30 import java.lang.management.ManagementFactory;
  31 import java.lang.management.ThreadMXBean;
  32 import java.util.Map;
  33 
  34 public class ThreadLists {
  35     public static void main(String args[]) {
  36 
  37         // Bug id : JDK-8151797
  38         // Use a lambda expression so that call-site cleaner thread is started
  39         Runnable printLambda = () -> {System.out.println("Starting Test");};
  40         printLambda.run();
  41 
  42         // get top-level thread group
  43         ThreadGroup top = Thread.currentThread().getThreadGroup();
  44         ThreadGroup parent;
  45         do {
  46             parent = top.getParent();
  47             if (parent != null) top = parent;
  48         } while (parent != null);
  49 
  50         // get the thread count
  51         int activeCount = top.activeCount();
  52 
  53         Map<Thread, StackTraceElement[]> stackTraces = Thread.getAllStackTraces();
  54 
  55         ThreadMXBean threadBean = ManagementFactory.getThreadMXBean();
  56         int threadCount = threadBean.getThreadCount();
  57         long[] threadIds = threadBean.getAllThreadIds();
  58 
  59         System.out.println("ThreadGroup: " + activeCount + " active thread(s)");
  60         System.out.println("Thread: " + stackTraces.size() + " stack trace(s) returned");
  61         System.out.println("ThreadMXBean: " + threadCount + " live threads(s)");
  62         System.out.println("ThreadMXBean: " + threadIds.length + " thread Id(s)");
  63 
  64         // check results are consistent
  65         boolean failed = false;
  66         if (activeCount != stackTraces.size()) failed = true;
  67         if (activeCount != threadCount) failed = true;
  68         if (activeCount != threadIds.length) failed = true;
  69 
  70         if (failed) {
  71             throw new RuntimeException("inconsistent results");
  72         }
  73     }
  74 }