The source contains make files which are used to compile the binaries. Switchs can be used to turn options in the build off and on. Build the version which accepts plug in modules, as you need to install Jserv to talk with Tomcat. Sun Perhaps the only Closed Source component in the system, I currently use Java 2. I had to download and install this for both my Linux and Windows systems.
Installation is simple, except for a gotcha or two on Linux.
There are competing JVM's, but I use the one from Sun for no particularly good reason. The JDK also comes with development environments such as Jbuilder from Inprise. Make sure that you delete the previous version of Java prior to installing the new one. Failure to do this may not result in immediate failure, but incompatibities between Java 1.1 and Java 1.2 will create runtime errors in Servlets. Don't have any classpath set at all.