Stepping through Statements of a Child Thread

Java Tools Tutorials - Herong's Tutorial Notes

∟Stepping through Statements of a Child Thread

This section provides a tutorial example on how to step through execution statements of the child thread in a multi-thread application.

2. Stepping through statements in the sub thread:

Thread-0[1] where all
Attach Listener:
Signal Dispatcher:
Finalizer:
  [1] java.lang.Object.wait (native method)
  [2] java.lang.ref.ReferenceQueue.remove (ReferenceQueue.java:142)
  [3] java.lang.ref.ReferenceQueue.remove (ReferenceQueue.java:158)
  [4] java.lang.ref.Finalizer$FinalizerThread.run (Finalizer.java:209)
Reference Handler:
  [1] java.lang.Object.wait (native method)
  [2] java.lang.Object.wait (Object.java:502)
  [3] java.lang.ref.Reference$ReferenceHandler.run (Reference.java:157)
main:
  [1] java.lang.Thread.sleep (native method)
  [2] PrimeNumberSeeker.main (PrimeNumberSeeker.java:21)
Thread-0:
  [1] PrimeNumberSeeker.run (PrimeNumberSeeker.java:28)

Thread-0[1] next
2, 2, 0
>
Step completed: "thread=Thread-0", PrimeNumberSeeker.run(), line=29
29          while (count < ceiling) {

Thread-0[1] where all
...
main:
  [1] java.lang.Thread.sleep (native method)
  [2] PrimeNumberSeeker.main (PrimeNumberSeeker.java:21)
Thread-0:
  [1] PrimeNumberSeeker.run (PrimeNumberSeeker.java:29)

Thread-0[1] next
3, 2, 0
> 
Step completed:
   "thread=Thread-0", PrimeNumberSeeker.run(), line=30 bci=17
30             current++;

Thread-0[1] next
4, 3, 0
>
Step completed:
   "thread=Thread-0", PrimeNumberSeeker.run(), line=31 bci=27
31             int j = 2;

Thread-0[1] next
5, 3, 0
>
Step completed: 
   "thread=Thread-0", PrimeNumberSeeker.run(), line=32 bci=29
32             boolean isPrime = true;

Thread-0[1] next
6, 3, 0
>
Step completed: 
   "thread=Thread-0", PrimeNumberSeeker.run(), line=33 bci=31
33             while (j<current/2 && isPrime) {

Thread-0[1] list
29          while (count < ceiling) {
30             current++;
31             int j = 2;
32             boolean isPrime = true;
33 =>          while (j<current/2 && isPrime) {
34                isPrime = current % j > 0;
35                j++;
36             }
37             if (isPrime) {
38                count++;
Thread-0[1] print current
 current = 3

What I have done here:

I used "where all" to display the current location of all threads.
Then I used "next" to execute one statement in the current thread, the sub thread, going from line 28 to line 29.
The next "where all" command showed me that the main thread went through an entire iteration of the "while" loop. The main thread stopped again at line 21.
Then I used a couple of "next" command in the sub thread to bring the execution to line 33. At the same time, the main thread went through a couple of iterations, printed some output messages.
Then I used "print" to check the current value of variable "current". Value 3 is correct.

Last update: 2015.

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About This Book

Java Tools Terminology

Installing Java 8 on Windows

'javac' - The Java Program Compiler

'java' - The Java Program Launcher

►'jdb' - The Java Debugger

'jdb' - Java Debugger Command and Options

Starting a Debugging Session with 'jdb'

Debugging Applications with Separate 'jdb' Sessions

Debugging Java Applications Remotely