The Sun Microsystems Java Developer's Kit (JDK) Version 1.2, is at http://java.sun.com/products/jdk/1.2/download-linux.html.
You can also get the source code, which is licensed by Sun Microsystems.
Kaffee, an Open-Source version of Java, is at http://www.transvirtual.com/products/.
The home page of IBM's Jikes Java compiler is http://www10.software.ibm.com/developerworks/opensource/jikes.
There is a version of Sun's HotJava browser for Linux at http://www.java.sun.com/products/hotjava/.
Netscape Communicator comes with its own version of the Java Runtime Environment, so if you need Java only to view Web graphics, you may already have the runtime version of the Java Virtual Machine and libraries that you need installed on your system. You can download Communicator from http://www.netscape.com/.