// This example is from the book _Java in a Nutshell_ by David Flanagan.
// Written by David Flanagan.  Copyright (c) 1996 O'Reilly & Associates.
// You may study, use, modify, and distribute this example for any purpose.
// This example is provided WITHOUT WARRANTY either expressed or implied.

import java.io.*;

public class ThreadLister {
    // Display info about a thread.
    private static void printThreadInfo(PrintStream out, Thread t, String indent) {
        if ( t == null ) 
          return;
        out.println(indent + "+--> Thread: " + t.getName() + "  Priority: " + t.getPriority() +
                (t.isDaemon()?" Daemon":"") + (t.isAlive()?"":" Not Alive"));
    }
    
    // Display info about a thread group and its threads and groups
    private static void listGroup(PrintStream out, ThreadGroup g, String indent) {
        if (g == null) return;
        int nrThreads = g.activeCount();
        int nrGroups  = g.activeGroupCount();
        Thread[]      threads = new Thread[nrThreads];
        ThreadGroup[] groups  = new ThreadGroup[nrGroups];
        
        g.enumerate(threads, false);
        g.enumerate(groups, false);
        
        out.println("\n" + indent + " Thread Group: " + g.getName() + "  Max Priority: " + 
                    g.getMaxPriority() + (g.isDaemon()?" Daemon":""));
        
        for(int i = 0; i < nrThreads; i++)
            printThreadInfo(out, threads[i], indent + "    ");
        for(int i = 0; i < nrGroups; i++)
            listGroup(out, groups[i], indent + "    ");
    }
    
    // Find the root thread group and list it recursively
    public static void listAllThreads(PrintStream out) {
        ThreadGroup currentThreadGroup;
        ThreadGroup rootThreadGroup;
        ThreadGroup parent;
        
        // Get the current thread group
        currentThreadGroup = Thread.currentThread().getThreadGroup();
        
        // Now go find the root thread group
        rootThreadGroup = currentThreadGroup;
        try {
        	while( true ) {
            rootThreadGroup.checkAccess();
       	    parent = rootThreadGroup.getParent();
            if( parent == null ) 
              break;
            rootThreadGroup = parent;
          }
        }
        catch( SecurityException e ) {
        	;
        }
        // And list it, recursively
        listGroup(out, rootThreadGroup, "");
    }    
    
    public static void main(String[] args) {
        ThreadLister.listAllThreads(System.out);
        try { 
        	Thread.sleep(200); 
        } catch (InterruptedException e) { 
          e.printStackTrace();	
        }

    }
}