[Bluej-discuss] Thread Question

[Mark Dutchuk (MALA)]

Hello folks.  I'm puzzled by a problem I am having with Threads and ThreadGroups.  I've distilled the problem down to the following program to demonstrate the problem:

public class TGTest {

    private static ThreadGroup threadGroup = new ThreadGroup("Some Thread Group");
    
    public static void myTest1() {
        
        EventOne e1 = new EventOne();
        // Create a new Thread running under the 'threadGroup' ThreadGroup
        new Thread(threadGroup, e1).start(); 
        
        EventTwo e2 = new EventTwo();
        new Thread(threadGroup, e2).start();
    }
    public static void myTest2() {
        EventOne e1 = new EventOne();
        new Thread(threadGroup, e1).start(); 
    }
}

class EventOne extends Thread {
    public void run() {
        System.out.println("EventOne: " + getThreadGroup());
    }
}

class EventTwo extends Thread {
    public void run() {
        TGTest.myTest2();
    }
}

Here's the output when I run TGTest.test1():

EventOne: java.lang.ThreadGroup[name=main,maxpri=10]
EventOne: java.lang.ThreadGroup[name=Some Thread Group,maxpri=10]


Why does EventOne run under the 'main' ThreadGroup when I call myTest1() directly from BlueJ, but under 'Some Thread Group' when EventTwo calls myTest1()?  I want it to run under 'Some Thread Group' both times, but I can't see the problem.

btw:  The problem has nothing to do with static methods and/or variables.  I've rewritten the program both ways (setting everything non-static and creating an instance of TGTest), the outcome is the same.  Any help or suggestions would be much appreciated.


dmd.
-- 
Donald (Mark) Dutchuk,
Instructor / Program Coordinator,
Information Technology Applied Systems (ITAS) Program
Malaspina University/College
Room 226 - Building 180
900 - 5th Street
Nanaimo, BC CAN  V9R 5S5
Telephone: (250) 740-6116