"Java, Sun SPOT and the FIRST Robotics Competition"

[jtdowney]

Originally Posted by Ice Berg

Can someone who knows more about this me give a few reasons why Java would be better or worse than c++.

In addition to what Greg mentioned I would add checked exceptions which would make it safe to use exceptions in WPILibJ because you can have the compiler force you to handle every exception. I know a lot of Java developers dislike checked exceptions but I believe this is one place where it is useful.

[gblake]

On the down side, Java will run quite a bit slower.

This might be a distinction without a difference - Depending on the Java Virtual Machine you are using, Java Byte Code can run plenty fast for plenty of applications - This only becomes important if you are running out of clock cycles - And, for my 2 cents, if I start doing any work likely to exhaust the clock cycles of a microcontroller, I'm going to want to offload the microcontroller (attach a fast General Purpose computer (a co-processor) to do the intense math or other heavy lifting).

Find out what speed you (really) REQUIRE before using speed as a selection criterion.

The garbage collection causes hiccups where the OS is doing something besides running your code.

In full fledged Java implementations, you can invoke garbage collection as often as you want. This doesn't explicitly prevent the VM from deciding to run it; but it does give you a chance minimize how often the VM will surprise you by cleaning up after yourself.

C++ probably has more robotics usage, so more code to borrow from.

Yes and no - I suspect that if you look at the robot code as the core of a large collection of general purpose development and debug code, and environments, you might find that there are plenty of Java infrastructure tools that make it worth your while to use Java. It is that infrastructure that
chews up most of my time when developing robot-ish software; not the robot software itself.

Or you might not

Blake

[ttldomination]

hm...I really like this idea. Now whether the programming team, mainly one guy, chooses to accept this idea, I'm pretty sure that all of a sudden, our programming base will expand simply because we have so many kids who are, or can be, good with Java. The school offers many classes not to mention I know for a fact that we have a couple of Java wizes in our school.


I like this. .

[mathking]

I teach high computer science, and we have used the RidgeSoft IntelliBrain robots in class, which are programmed in Java.

Aside from the exception handling which has been mentioned, I would absolutely add event handling. Programming multiple sensors with the IntelliBrain (which has a MUCH more limited processor than the cRIO) is easy because of the way Java handles events. When I first learned Java (when the AP CS course moved from C++ to Java) the event and exception handling were among the first really cool things I noticed about Java.

As for speed, I agree with gblake. It really depends on how you compile the code Running robots in the standard JVM would be slow. But I have written plenty of programs for OS X using XCode to compile Cocoa native applications for the Macintosh, and they run just as fast as Objective-C programs.

As for tools, there may be a relative lack of robot specific libraries for Java, but there are some. Mindstorms and the aforementioned IntelliBrain robots can be programmed in Java. There are other platforms that use Java as well.

The biggest thing to remember is that this is an addition. You don't have to use Java if you don't want to. But it will open up programming to more students, because Java is the language most will have learned in their HS computer science classes.

[nathanww]

On one hand, this is cool. I use Java, I like Java, I think Java is a great language.

On the other hand: ANOTHER PROGRAMMING SYSTEM???!!!! That means that I get to go through the whole C++/C/labVIEW decision process again, and if we decide to use it help bring the programming team up to speed on a new IDE, language, etc.

[ttldomination]

nathanww has a certain point and for teams who are still jumping around with programming have yet another option.

But for us, bringing kids up to par with the programming won't be so hard considering that the school has a curriculum in place for this already.

[virtuald]

Actually, I believe the java stuff could use eclipse also, so no changing IDE's.

[EricVanWyk]

Originally Posted by nathanww

On one hand, this is cool. I use Java, I like Java, I think Java is a great language.

On the other hand: ANOTHER PROGRAMMING SYSTEM???!!!! That means that I get to go through the whole C++/C/labVIEW decision process again, and if we decide to use it help bring the programming team up to speed on a new IDE, language, etc.

Get used to it - we have enough tricks up enough sleeves to power an innovation revolution, and we ain't stopping until each of your sleeves are full!

[byteit101]

Originally Posted by virtuald

Actually, I believe the java stuff could use eclipse also, so no changing IDE's.

even if it does use eclipse (the base of Windriver), there will definably be some differences, (like a cRIO connection thing) so you will have to learn some more stuff (though generally the same)

[daneelshof]

Java is what they use mainly where I go to college for CS, and I think this is partly because it is a more homogenous system for teaching than C or C++, where there could be many compilers and oddities between OSes (BTW, there is about an even mix of Linux, Windows, and OS X amongst the CS students there.)

Sun SPOTS are really interesting looking devices, but I think they have been poorly marketed. Anyway, they seem to handle Java in real-time pretty well, they are being used in a couple of cases as sensor networks. From what I can deduce from the press releases and the Java on FIRST website (http://sunspotworld.com/frc/Welcome.html) they will implement Java similarly. The Sun SPOTS have an ARM processor (the cRIO, a Freescale PPC) and they use the Squawk VM, which is specifically designed for embedded apps. This VM is running right on top of the hardware, so the user code isn't that far from the hardware. It certainly isn't farther from the hardware than VxWorks or LabVIEW, so Java code might be quicker than these methods, but that remains to be seen.

As for Garbage Collection, each virtual machine has to implement that, thus Squawk's is almost certainly different than the 'typical' Java VM. From their site, they say they have three methods for GC which are user selectable (although they may not be in our case.)

One successful example of using Java in robots is Basil (Google Jim and Louise Gunderson.) They've got a few Javelin stamps wired to a *ton* of sensors and outputs. There are countless other examples too. I believe there are a couple of hardware Java VMs too.

A few students have shown interest in learning Java on my team, and I'm planning on holding class sessions during the summer. We transitioned directly from C to LabVIEW, so a major part of the class will be OO concepts.

Sorry for the dissertation, but hopefully this is useful.