Being a java developer I was intrigued with the idea of getting a JVM running on my NSLU2, so I looked into how to do this.

Surprisingly it was pretty easy.

To start with you need to install the following packages with ipkg:

ipkg install classpath

ipkg install jamvm

ipkg install jikes

ipkg install zlib

ipkg install file

Once these have installed then you are almost ready to go.  Being a java developer, I was used to using javac and java to compile and execute programs, so jikes and jamvm didn’t sit well with me!  To get around this I created a symbolic link and a shell script in /opt/bin

These are as follows:

/opt/bin/java

 ln -s /opt/bin/jamvm /opt/bin/java

/opt/bin/javac

/opt/bin/jikes -classpath /opt/share/jamvm/classes.zip:/opt/share/classpath/glibj.zip $*

Remember to change the permissions on the shells scripts to add the execute flag!

Having  done all that, I can now create a java file:

HelloWorld.java

class HelloWorld

{

     public static void main(String[] args)

     {

          System.out.println("Pembo's Hello World!");

          System.out.println("Args Length: " + args.length);

          for(int i=0;i<args.length;i++)

          {

               System.out.println("[" + i + "] - " + args[i]);

          }

     }

}

compile this using the command

javac HelloWorld.java

and then run this using the command

java HelloWord test1 test2 test3

And I see the following output:

Pembo's Hello World!

Args Length: 4

[0] - test1

[1] - test2

[2] - test3

JamVM is excellent from what I’ve seen so far and is perfect for Java NSLU2 development.
I’ve yet to run anything overly complex on the Slug so I can’t comment on the memory utilisation.

It takes around a second to compile the above HelloWorld program on the NSLU2 and under a second to run it.