Monitoring java threads programmatically

Using the java.lang.management package introduced in java 1.5 one may monitor some aspects of the threads of a java process:

• Find all active threads and get their stack traces
• Find deadlocked threads
• Find out what lock a thread is waiting for (and which thread owns it)
  
• (Optional, depending on JVM): Monitor thread contention - how many times and for how long have each thread waited or blocked
• (Optional, depending on JVM): Measure thread CPU time (and how much of that time was spent in user mode)

The code to do this looks as follows:

ThreadMXBean threadBean = ManagementFactory.getThreadMXBean();
if (threadBean.isThreadCpuTimeSupported())
    threadBean.setThreadCpuTimeSupported(true);
if (threadBean.isThreadContentionMonitoringSupported())
    threadBean.setThreadContentionMonitoringEnabled(true);

out.println("There are " + threadBean.getThreadCount() +
    " threads of which " + threadBean.getDaemonThreadCount() +
    " are daemons.");

ThreadInfo[] infos
    = threadBean.getThreadInfo(threadBean.getAllThreadIds(), Integer.MAX_VALUE);

for (ThreadInfo info : infos) {
    out.println("Thread(id=" + info.getThreadId() + "): " +
        info.getThreadName() + ":");

    out.println("\tState: " + info.getThreadState());
    if (info.getLockOwnerId() != null)
        out.println("\tWaiting on lock " + info.getLockName() + " owned by " + info.getLockOwnerId());

    if (info.getBlockedTime() != -1) {
        out.println("\tBlocked time: " + (info.getBlockedTime() / 1000.) + " seconds during " +
            info.getBlockedCount() + " blocks");
        out.println("\tWaited time: " + (info.getWaitedTime() / 1000.) + " seconds during " +
            info.getWaitedCount() + " blocks");
    }

    out.println("\tStack trace:");
    for (int j = 0; j < threadInfo.getStackTrace().length; j++) {
        StackTraceElement e = threadInfo.getStackTrace()[j];
        out.println(e.getClassName() + "#" + e.getMethodName() + ":" + e.getLineNumber());
    }
}