Classloader exception in Java debugger built using JDI - Please reply

Question

Im a newbie to java & ive been trying to develop a simple java debugger & ive been getting the following set of exception ir-respective of ip file given to debug
Exception:::java.lang.ClassLoader.loadClass(java.lang.String, boolean)
Exception:::java.lang.ClassLoader.loadClass(java.lang.String, boolean)
Exception:::java.lang.ClassLoader.loadClass(java.lang.String, boolean)
Exception in thread "Thread-0" java.util.NoSuchElementException
at com.sun.tools.jdi.EventSetImpl$Itr.next(EventSetImpl.java:822)
at com.sun.tools.jdi.EventSetImpl$Itr.nextEvent(EventSetImpl.java:827)
at jds.Executepgm.run(Executepgm.java:48)
Can someone reply please its very urgent
ive attached the code here
MAIN CLASS
package jds;
import com.sun.jdi.VirtualMachine;
import java.io.*;
public class JDS {
public static void main(String[] args) {
if(args.length == 0 || args[0].equalsIgnoreCase("-help")|| args.length>1)
help();
System.exit(0);
LaunchVM lvm = new LaunchVM();
String str= new String();
str = readstr();
if (str.contains("run"))
String str2 =new String();
try
str2 = args[0]+str.substring(3);
catch(StringIndexOutOfBoundsException e)
str2=args[0];
VirtualMachine vm = lvm.launchTarget(str2);
vm.setDebugTraceMode(0);
Executepgm expm =new Executepgm(vm);
System.out.println("run cmd");
expm.runpgm(vm);
expm.start();
vm.resume();
static void help() {
     System.out.println("**Usage: java JDS <class> **");
static String readstr()
String str = new String();
BufferedReader stdin = new BufferedReader(new InputStreamReader(System.in));
try
str= stdin.readLine();
catch (IOException ioe) {
System.out.println("Recieved exception: "+ioe);
System.exit(1);
return str;
SUPPORT CLASS
package jds;
import com.sun.jdi.*;
import com.sun.jdi.event.*;
import com.sun.jdi.request.*;
public class Executepgm extends Thread{
private VirtualMachine vm;
String[] excludes = {"java.*", "javax.*", "sun.*",
                    "com.sun.*"};
Executepgm(VirtualMachine vm)
this.vm=vm;
public void run()
EventQueue queue = vm.eventQueue();
boolean connected = true;
while(connected == true)
try {
EventSet eventSet = queue.remove();
EventIterator it = eventSet.eventIterator();
while (it.hasNext()) {
Event et=it.nextEvent();
if(et instanceof MethodEntryEvent)
System.out.println("method entry"+et);
else if (et instanceof MethodExitEvent)
System.out.println("method exit"+et);
else if (et instanceof ExceptionEvent)
try
System.out.println("Exception:::"+((ExceptionEvent)et).catchLocation().method());
catch(NullPointerException e)
et=it.nextEvent();
else if(et instanceof VMDisconnectEvent)
connected = false;
eventSet.resume();
} catch (InterruptedException exc) {
System.out.println("Interrupted");
} catch (VMDisconnectedException discExc) {
void runpgm(VirtualMachine vm)
EventRequestManager erm = vm.eventRequestManager();
ExceptionRequest excReq = erm.createExceptionRequest(null,true, true);
excReq.setSuspendPolicy(EventRequest.SUSPEND_ALL);
excReq.enable();
MethodEntryRequest menr = erm.createMethodEntryRequest();
for (int i=0; i<excludes.length; ++i) {
menr.addClassFilter(excludes);
menr.setSuspendPolicy(EventRequest.SUSPEND_NONE);
menr.enable();
MethodExitRequest mexr = erm.createMethodExitRequest();
for (int i=0; i<excludes.length; ++i) {
mexr.addClassFilter(excludes[i]);
mexr.setSuspendPolicy(EventRequest.SUSPEND_NONE);
mexr.enable();

Answer 1

The program under test is throwing exceptions. Your code catches these exceptions and prints out
Exception:::.................
You should change your code to print out the kind of exception and the stack trace associated with the exception to see where it is coming from (ie, the call stack for the loadClass method that is throwing the exception.
Note that you are getting both caught and uncaught exceptions. You will probably find that these exceptions are part of the normal class loading process, and that they are caught and handled by the class loader. You can change your code to not request caught exceptions if you don't want to get these.