java threads

[jignesh soni]

which are the two threads always running in java ?

[Norm Radder]

I give up.
Is it the white one and the black one?

[Ulf Dittmer]

Here's some code that will come in handy if you want to investigate what threads are active at any given time.

    private void getThreadInfo (PrintWriter output)
    {
        // Get the top level thread group
        ThreadGroup adam = getAdam(Thread.currentThread().getThreadGroup());
        // Get the count of active threads in the system
        int num = adam.activeCount();
 
        // Get all of the active threads in the system
        Thread list[] = new Thread[num];
        int x = adam.enumerate(list);
// if (x != num)
//return;
 
        // Display all of the active threads in the system
        output.println("<p><b>Threads</b><table border=1><tr>");
        output.println("<th>Group</th><th>Name</th><th>Priority</th><th>Daemon</th><th>Alive</th></tr>");
 
        for (int i = 0; i < x; i++)
        {
            if (list[i] == null) continue;
            String threadName = list[i].getName();
            String groupName = list[i].getThreadGroup().getName();
            output.println("<tr><td>" + groupName
                    + "</td><td>" + threadName
                    + "</td><td>" + list[i].getPriority()
                    + "</td><td>" + (list[i].isDaemon() ? "Yes" : "No")
                    + "</td><td>" + (list[i].isAlive() ? "Yes" : "No")
                    + "</td></tr>");
        }
        output.println("</table>");
    }
 
    // Recursively calls itself to find the top level thread group
    private ThreadGroup getAdam (ThreadGroup tg)
    {
        ThreadGroup parent = tg.getParent();
        if (parent == null)
            return tg;
 
        return getAdam(parent);
    }

[Nitesh Kant]

Alternatively, take a thread dump(CTRL-Break(Win systems) or CTRL-/(Unix)) and find it for yourself how many threads are alive and they are in what states!!