Examples of java.lang.management.ThreadMXBean

java.lang.management.ThreadMXBean
The management interface for the thread system of the Java virtual machine.
A Java virtual machine has a single instance of the implementation class of this interface. This instance implementing this interface is an MXBean that can be obtained by calling the {@link ManagementFactory#getThreadMXBean} method orfrom the {@link ManagementFactory#getPlatformMBeanServer platform MBeanServer} method.
The ObjectName for uniquely identifying the MXBean for the thread system within an MBeanServer is:
{@link ManagementFactory#THREAD_MXBEAN_NAME java.lang:type=Threading}

Thread ID
Thread ID is a positive long value returned by calling the {@link java.lang.Thread#getId} method for a thread.The thread ID is unique during its lifetime. When a thread is terminated, this thread ID may be reused.
Some methods in this interface take a thread ID or an array of thread IDs as the input parameter and return per-thread information.
Thread CPU time
A Java virtual machine implementation may support measuring the CPU time for the current thread, for any thread, or for no threads.
The {@link #isThreadCpuTimeSupported} method can be used to determineif a Java virtual machine supports measuring of the CPU time for any thread. The {@link #isCurrentThreadCpuTimeSupported} method can be used to determine if a Java virtual machine supports measuring of the CPU time for the current thread. A Java virtual machine implementation that supports CPU time measurement for any thread will also support that for the current thread.
The CPU time provided by this interface has nanosecond precision but not necessarily nanosecond accuracy.
A Java virtual machine may disable CPU time measurement by default. The {@link #isThreadCpuTimeEnabled} and {@link #setThreadCpuTimeEnabled}methods can be used to test if CPU time measurement is enabled and to enable/disable this support respectively. Enabling thread CPU measurement could be expensive in some Java virtual machine implementations.
Thread Contention Monitoring
Some Java virtual machines may support thread contention monitoring. When thread contention monitoring is enabled, the accumulated elapsed time that the thread has blocked for synchronization or waited for notification will be collected and returned in the ThreadInfo object.
The {@link #isThreadContentionMonitoringSupported} method can be used to determine if a Java virtual machine supports thread contention monitoring. The thread contention monitoring is disabled by default. The {@link #setThreadContentionMonitoringEnabled} method can be used to enablethread contention monitoring.
Synchronization Information and Deadlock Detection
Some Java virtual machines may support monitoring of {@linkplain #isObjectMonitorUsageSupported object monitor usage} and{@linkplain #isSynchronizerUsageSupported ownable synchronizer usage}. The {@link #getThreadInfo(long[],boolean,boolean)} and {@link #dumpAllThreads} methods can be used to obtain the thread stack traceand synchronization information including which {@linkplain LockInfo lock} a thread is blocked toacquire or waiting on and which locks the thread currently owns.
The ThreadMXBean interface provides the {@link #findMonitorDeadlockedThreads} and {@link #findDeadlockedThreads} methods to find deadlocks inthe running application. @see JMX Specification. @see Ways to Access MXBeans @author Mandy Chung @version 1.20, 03/08/06 @since 1.5

  /**
   * Count the number of threads that have a stack frame containing
   * the given string
   */
  private static int countThreads(String search) {
    ThreadMXBean threadBean = ManagementFactory.getThreadMXBean();


    int count = 0;
    ThreadInfo[] infos = threadBean.getThreadInfo(threadBean.getAllThreadIds(), 20);
    for (ThreadInfo info : infos) {
      if (info == null) continue;
      for (StackTraceElement elem : info.getStackTrace()) {
        if (elem.getClassName().contains(search)) {
          count++;

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        future.join();


        c1.set( future.getSession() );
        ((IoSession) c1.get()).write( "start" );


        ThreadMXBean threadMXBean = ManagementFactory.getThreadMXBean();


        while ( !messageCount.await( 100, TimeUnit.MILLISECONDS ) ) {
            long[] threads = threadMXBean.findMonitorDeadlockedThreads();


            if ( null != threads ) {
                StringBuffer sb = new StringBuffer( 256 );
                ThreadInfo[] infos = threadMXBean.getThreadInfo( threads, Integer.MAX_VALUE );


                for (int i = 0; i < infos.length; i ++) {
                    ThreadInfo info = infos[i];
                    sb.append( info.getThreadName() )
                        .append( " blocked on " )

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    stats.add(new StatRecord(getName(), "Load average", "double",
            format.format(osBean.getSystemLoadAverage()), Level.INFO));
    stats.add(new StatRecord(getName(), "CPUs no", "int",
            osBean.getAvailableProcessors(), Level.FINEST));


    ThreadMXBean thBean = ManagementFactory.getThreadMXBean();
    stats.add(new StatRecord(getName(), "Threads count", "int",
            thBean.getThreadCount(), Level.FINEST));
    long cpuTime = 0;
    for (long thid : thBean.getAllThreadIds()) {
      cpuTime += thBean.getThreadCpuTime(thid);
    }
//    stats.add(new StatRecord(getName(), "Threads CPU time", "long", cpuTime,
//        Level.FINEST));
    double cpuUsage = (new Long(cpuTime).doubleValue() / 1000000) / new Long(
            uptime).doubleValue();

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   * 
   * @return an array of threads
   */
  public static Thread[] getAllThreads() {
    final ThreadGroup root = getRootThreadGroup();
    final ThreadMXBean thbean = ManagementFactory.getThreadMXBean();
    int nAlloc = thbean.getThreadCount();
    int n = 0;
    Thread[] threads = null;
    do {
      nAlloc *= 2;
      threads = new Thread[nAlloc];

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   * Get a list of all thread info objects. Since there is always at least one thread running, there is always at least one thread info object. This method never returns a null or empty array.
   * 
   * @return an array of thread infos
   */
  public static ThreadInfo[] getAllThreadInfos() {
    final ThreadMXBean thbean = ManagementFactory.getThreadMXBean();
    final long[] ids = thbean.getAllThreadIds();


    // Get thread info with lock info, when available.
    ThreadInfo[] infos;
    if (!thbean.isObjectMonitorUsageSupported() || !thbean.isSynchronizerUsageSupported())
      infos = thbean.getThreadInfo(ids);
    else
      infos = thbean.getThreadInfo(ids, true, true);


    // Clean nulls from array if threads have died.
    final ThreadInfo[] notNulls = new ThreadInfo[infos.length];
    int nNotNulls = 0;
    for (ThreadInfo info : infos)

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    }


    /** thread CPU time in milliseconds. */
    private long getCpuTimeInMillis ()
    {
        ThreadMXBean bean = ManagementFactory.getThreadMXBean();
        return bean.isCurrentThreadCpuTimeSupported() ? bean.getCurrentThreadCpuTime()/1000000: 0L;
    }

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        future.await();


        c1.set(future.getSession());
        c1.get().write("start");


        ThreadMXBean threadMXBean = ManagementFactory.getThreadMXBean();


        while (!messageCount.await(100, TimeUnit.MILLISECONDS)) {
            long[] threads = threadMXBean.findMonitorDeadlockedThreads();


            if (null != threads) {
                StringBuffer sb = new StringBuffer(256);
                ThreadInfo[] infos = threadMXBean.getThreadInfo(threads, Integer.MAX_VALUE);


                for (ThreadInfo info : infos) {
                    sb.append(info.getThreadName())
                            .append(" blocked on ")
                            .append(info.getLockName())

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    /*
     * Test method for
     * 'java.lang.management.ManagementFactory.getThreadMXBean()'
     */
    public void testGetThreadMXBean() {
        ThreadMXBean mb = ManagementFactory.getThreadMXBean();
        assertNotNull(mb);


        // Verify that there is only instance of this bean
        ThreadMXBean mb2 = ManagementFactory.getThreadMXBean();
        assertNotNull(mb2);
        assertSame(mb, mb2);
    }

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        // Named MXBean does not implement the supplied MXBean interface
        List<GarbageCollectorMXBean> allGCBeans = ManagementFactory
                .getGarbageCollectorMXBeans();
        for (GarbageCollectorMXBean bean : allGCBeans) {
            try {
                ThreadMXBean proxy = ManagementFactory.newPlatformMXBeanProxy(
                        ManagementFactory.getPlatformMBeanServer(), bean
                                .getName(), ThreadMXBean.class);
                fail("should have thrown IllegalArgumentException");
            } catch (IllegalArgumentException ignore) {
            }
        }// end for


        // Named MXBean does not implement the supplied MXBean interface
        List<MemoryManagerMXBean> allMMBeans = ManagementFactory
                .getMemoryManagerMXBeans();
        for (MemoryManagerMXBean bean : allMMBeans) {
            try {
                ThreadMXBean proxy = ManagementFactory.newPlatformMXBeanProxy(
                        ManagementFactory.getPlatformMBeanServer(), bean
                                .getName(), ThreadMXBean.class);
                fail("should have thrown IllegalArgumentException");
            } catch (IllegalArgumentException ignore) {
            }

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     * Test method for
     * 'java.lang.management.ManagementFactory.newPlatformMXBeanProxy(MBeanServerConnection,
     * String, Class<T>) <T>'
     */
    public void testNewPlatformMXBeanProxy_ThreadMXBean() throws Exception {
        ThreadMXBean proxy = ManagementFactory.newPlatformMXBeanProxy(
                ManagementFactory.getPlatformMBeanServer(),
                "java.lang:type=Threading", ThreadMXBean.class);
        assertNotNull(proxy);
        ThreadMXBean mb = ManagementFactory.getThreadMXBean();
        // Not an exhaustive check...
        assertEquals(mb.isCurrentThreadCpuTimeSupported(), proxy
                .isCurrentThreadCpuTimeSupported());
        assertEquals(mb.isThreadContentionMonitoringSupported(), proxy
                .isThreadContentionMonitoringSupported());
        assertEquals(mb.isThreadCpuTimeSupported(), proxy
                .isThreadCpuTimeSupported());
        ThreadInfo info1 = mb.getThreadInfo(Thread.currentThread().getId());
        ThreadInfo info2 = proxy.getThreadInfo(Thread.currentThread().getId());
        // RI does not appear to override equals() for ThreadInfo so we take
        // the scenic route to check for equality...
        assertEquals(info1.getThreadId(), info2.getThreadId());
        assertEquals(info1.getBlockedCount(), info2.getBlockedCount());

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Examples of java.lang.management.ThreadMXBean

Thread ID

Thread CPU time

Thread Contention Monitoring

Synchronization Information and Deadlock Detection

Related Classes of java.lang.management.ThreadMXBean