From the command line or with an IDE?

Either way it's pretty much the same as it is on Windows and Linux,  
assuming the tools are all installed.  Are you familiar with a UNIX-style  
shell?  The default shell on Solaris is not much fun (backspace and  
command history don't work as you would expect), but you can replace it  
for the remainder of the session with bash or some other shell of your  
choosing (you need root access to edit /etc/passwd to change it  
permanently).  To switch to bash run:

    exec bash

Solaris 10 comes with the JDK pre-installed.  So from the command line you  
can run:

    java -version

And this will tell you what version you have (or give you an error if  
there is no java on the path).

Are you familiar with the JDK's command line tools on another platform?  
The java and javac tools work just as they do in Windows and Linux:

    javac HelloWorld.java
    java HelloWorld

Dan.