Java Questions

I’m trying to get a sense of what the capabilities of the new Java platform are going to be. I’d love any help those who know might be able to provide to any of the following questions.

  1. Is it easy to see the output from System.out.println() on your PC?

  2. What happens when your Java program throws an Exception? Do you get the Exception message and stack trace on your PC?

  3. Does remote debugging (breakpoints, watching variables) work?

  4. Assuming that they are available, has anyone tried using Java’s Threads on a cRio? Does they work well?

  5. We’ve heard that the Java system we will be using for FRC is based on the Java ME edition, but Java ME comes in two configurations (CLDC and CDC) and I haven’t heard anyone specify which we will be using. As I understand it, the system we’re using is based on Squawk, which in turn claims to be CLDC 1.1 compatible, but it would be nice to have this confirmed from someone who knows for sure.

The CLDC 1.1 (JSR 139) configuration (documented here: has classes like Thread, Vector, Hashtable, Random, and a Math class with floating point functions).

The older CLDC 1.0 (JSR 30) configuration (documented here: has a Math class without any floating point functions like sin, cos, etc.

The much richer CDC 1.1.2 (JSR 218) configuration (documented here: has many more classes, including (for example) ArrayList, LinkedList, HashMap, TreeMap, HashSet, TreeSet, BitSet, etc.

Thanks in advance for any help you can provide. I’m the software mentor for my team and I’d like to give my students a clearer picture of what the FRC Java system will be like.

Andrew Merrill
Software Mentor for team 1540, the Flaming Chickens

Hi Andrew,

In the future please post your questions in the official Java Beta Test FIRST Forum so that all teams and beta testers can see them:

I have posted your questions (and my answers to them) on that forum, but my post is awaiting moderator approval before showing up.


(The quick version of my answers:

  1. Yes
  2. Yes, sent to PC.
  3. Not sure; haven’t tried
  4. Yes, they work fine.
  5. Java ME is a minimal specification. Believe Squawk’s documentation, but there are some extras as well)

Thanks for the quick reply! BTW, yesterday I did post these questions to the official Java Beta Test Forum, but this morning someone deleted my post, which is why I reposted the questions here. Is there a rule that non-beta-test members can’t post to the Official Beta Test Forum?

Andrew Merrill
Software Mentor for team 1540, the Flaming Chickens

There isn’t any such rule. It looks like the FIRST forums are having problems which caused a lot of posts to be deleted, not just yours.

FYI – Remote debugging does exist and work in the FRC Java Beta system. It can be enabled really easily through Netbeans.

We are having problems getting the debugger to work.

File SQUAWK_DEBUG_ENABLED not found, starting squawk in normal mode…
Squawk command line file SQUAWK_COMMAND_LINE not found, using default args…

Anyone else having the same issues that solved this?

There is a bug in the current version of Java in the debug, it will be fixed shortly.