Non-static version of java.lang.Thread.dumpstack?

Question

hi,
it would be useful sometimes to have a graphical debug panel on an application I'm working on which shows the active threads and allows further information to be shown if wanted - the problem is that I can't find an API call to get the current stack dump of an arbitrary thread - does anyone know if this is possbile somehow without a full debug environment?
java.lang.Thread.dumpstack would be ideal if only it were an instance method..
thanks,
asjf

Answer 1

what's the probelm? you call this in the threads class
and each thread (object) executes this statement and
therefore prints its stacktrace ...ok - here is some mocked up (and plain wrong in terms of the tree model's consistency over sequential method calls) code that shows what I'd like to achieveimport java.io.*;
import java.util.*;
import javax.swing.*;
import javax.swing.tree.*;
import java.awt.*;
import javax.swing.event.*;
public class JThreadExp extends JPanel {
   JTree tree;
   JTextArea jta;
   public JThreadExp(TreeModel model) {
      super(new GridLayout(1,2,4,4));
      tree = new JTree(model);
      jta = new JTextArea();
      add(tree);
      add(jta);
      tree.addTreeSelectionListener(new TreeSelectionListener() {
         public void valueChanged(TreeSelectionEvent e) {
            PrintStream stderr = System.err;
            String msg=null;
            try {
               TreePath tp = e.getPath();
               System.out.println(tp.getLastPathComponent());
               ByteArrayOutputStream baos = new ByteArrayOutputStream();
               PrintStream ps = new PrintStream(new BufferedOutputStream(baos, 1024*1024));
               System.setErr(ps);
               Thread t = (Thread) tp.getLastPathComponent();
               try {
                  t.dumpStack();
               } catch(Throwable ee) {}
               ps.close();
               jta.setText(baos.toString()); //newXML.toString());
            } catch(Exception e2) {
               msg = e2.getMessage();
            System.setErr(stderr);
            if(msg!=null)
               System.out.println(msg);
   public static void main(String[]arg) throws Exception {
      JFrame frame = new JFrame("JThreadExp");
      JThreadExp jte;
      final ThreadModel tm = new ThreadModel();
      frame.getContentPane().add(jte = new JThreadExp(tm));
      frame.pack();
      frame.setVisible(true);
      final JTree tree = jte.tree;
      new Thread(new Runnable() {
         public void run() {
            try {
               while(true) {
                  TreeModelEvent tme = new TreeModelEvent(this, new Object [] {tm.getRoot()});
                  for(Iterator i = tm.listeners.iterator(); i.hasNext(); )
                     ((TreeModelListener) i.next()).treeStructureChanged(tme);
                  Thread.sleep(5000);
                  new Thread(new Runnable() {
                     public void run() {
                        try { Thread.sleep(50000); } catch(Exception e) {e.printStackTrace();}
                  } ).start();
            } catch(Exception e) {
               e.printStackTrace();
      } ).start();
class ThreadModel implements TreeModel {
   public boolean isLeaf(Object node) { return (node instanceof Thread); }
   public Object getRoot() {
      ThreadGroup uppermost = Thread.currentThread().getThreadGroup();
      while(uppermost.getParent()!=null)
        uppermost = uppermost.getParent();
      return uppermost;
   public Object getChild(Object p, int i) {
      Object result = "<unavailable>";
      if(p instanceof ThreadGroup) {
         ThreadGroup parent = (ThreadGroup) p;
         ThreadGroup[] tg = new ThreadGroup[parent.activeGroupCount()];
         Thread[] t = new Thread[parent.activeCount()];
         parent.enumerate(tg, false);
         parent.enumerate(t, false);
         if(i<tg.length)
            result = tg;
else if(i<tg.length+t.length)
result = t[i-tg.length];
return result;
public int getChildCount(Object node) {
int result = 0;
if(node instanceof ThreadGroup) {
ThreadGroup parent = (ThreadGroup) node;
ThreadGroup[] tg = new ThreadGroup[parent.activeGroupCount()];
Thread[] t = new Thread[parent.activeCount()];
result += parent.enumerate(tg, false);
result += parent.enumerate(t, false);
return result;
public int getIndexOfChild(Object parent, Object child) {
for(int i=0; i<getChildCount(parent); i++) {
if(getChild(parent,i).equals(child))
return i;
return -1;
Set listeners = new HashSet();
public void addTreeModelListener(TreeModelListener l) {
listeners.add(l);
public void removeTreeModelListener(TreeModelListener l) {
listeners.remove(l);
public void valueForPathChanged(TreePath path, Object newValue) { // this shouldn't be called - Tree is not editable
System.out.println("valueForPathChanged");
} The problem is that I'd like to obtain a reference to a Thread object (which I haven't written the code for) and get a (vaguely accurate if not exact) stack dump from it.
I'll have a look over JDB in the meantime thanks :)
thanks,
asjf