multithreading - Deadlock detection in Java

Question

Long time ago, I saved a sentence from a Java reference book: "Java has no mechanism to handle deadlock. it won't even know deadlock occurred." (Head First Java 2nd Edition, p.516)

So, what is about it? Is there a way to catch deadlock case in Java? I mean, is there a way that our code understands a deadlock case occurred?

Answer 1

Since JDK 1.5 there are very useful methods in the java.lang.management package to find and inspect deadlocks that occurs. See the findMonitorDeadlockedThreads() and findDeadlockedThreads() method of the ThreadMXBean class.

A possible way to use this is to have a separate watchdog thread (or periodic task) that does this.

Sample code:

  ThreadMXBean tmx = ManagementFactory.getThreadMXBean();
  long[] ids = tmx.findDeadlockedThreads();
  if (ids != null) {
     ThreadInfo[] infos = tmx.getThreadInfo(ids, true, true);
     System.out.println("The following threads are deadlocked:");
     for (ThreadInfo ti : infos) {
        System.out.println(ti);
     }
  }