We get different output in TL_PIT JDK when running following test.

% cat ThreadGroup.java
class ThreadGroup {
                                                                                                                                        
    public static void main(String args[]) {
                                                                                                                                        
        java.lang.ThreadGroup grp = Thread.currentThread().getThreadGroup();
        for(int i=0;i<5;i++) {
           java.lang.ThreadGroup g = new java.lang.ThreadGroup(grp,"Group-"+i);
           grp =g;
        }
        for (int i=0;i<10;i++) new Thread("New Thread"+i);
        Thread.currentThread().getThreadGroup().list();
    }
}
                                                                                                                                        
% /import/java/jdk1.5.0/solaris-sparc/bin/java ThreadGroup
java.lang.ThreadGroup[name=main,maxpri=10]
    Thread[main,5,main]
    Thread[New Thread0,5,main]
    Thread[New Thread1,5,main]
    Thread[New Thread2,5,main]
    Thread[New Thread3,5,main]
    Thread[New Thread4,5,main]
    Thread[New Thread5,5,main]
    Thread[New Thread6,5,main]
    Thread[New Thread7,5,main]
    Thread[New Thread8,5,main]
    Thread[New Thread9,5,main]
    java.lang.ThreadGroup[name=Group-0,maxpri=10]
        java.lang.ThreadGroup[name=Group-1,maxpri=10]
            java.lang.ThreadGroup[name=Group-2,maxpri=10]
                java.lang.ThreadGroup[name=Group-3,maxpri=10]
                    java.lang.ThreadGroup[name=Group-4,maxpri=10]
                                                                                                                                        
% /net/vmsqe/export/pit/tiger/ADHOCK/JDK/latest/solaris-sparc/bin/java ThreadGroup
java.lang.ThreadGroup[name=main,maxpri=10]
    Thread[main,5,main]
    java.lang.ThreadGroup[name=Group-0,maxpri=10]
        java.lang.ThreadGroup[name=Group-1,maxpri=10]
            java.lang.ThreadGroup[name=Group-2,maxpri=10]
                java.lang.ThreadGroup[name=Group-3,maxpri=10]
                    java.lang.ThreadGroup[name=Group-4,maxpri=10]