I think Java 1.1.x should have come with any version of Warp 4, and Java 1.1.8 should be part of a base eCS install. If for some reason you don't seem to have java 1.1.8 properly installed, you can download it from the Software Choice page for free. The link is here:
Just follow the links for the developer kit, and you will be able to downoad a runtime version as well. If it turns out that you do have Java 1.1.8 already installed, it may need to be updated. Type 'java -fullversion' at a command prompt to see the version of your defult JVM. The current 1.1.8 should return something like:
JAVA.EXE full version "JDK 1.1.8 IBM build o118-20011106 (JIT enabled: javax V3.5-IBMJDK1.1-20011106)"
You can update your Java 1.1.8 here:
for normal use, just download the runtime.exe, and execute it from the root of your boot drive.
If you install the Java 1.3.1, I would recommend against making it the default JVM. Several things, like TCP/IP configuration use the Java 1.1.8, and won't run properly by defaut with the newer Java installed as the default JVM.