The iSeries supports a fully functional Java Development Kit (JDK), which includes a java compiler and behaves very similar to a Unix-based Java platform when running inside the QSH environment.
Java was developed by Sun Microsystems as a platform independent programming language which does not run on a specific CPU or operating system, but on a JavaVirtualMachine which uses modern compilation techniques and on-the-profiling to give performance close to what is achievable in C++ and similar languages. See Java Performance Tuning for details on tuning Java performance on the IBM i.
Most Java applications can run on an iSeries, either as "headless" or using an X11 server (either Xvnc on the iSeries itself with a vncviewer locally, or a X11 server like wiredx.org or any modern Unix distribution).
For web applications not needing the full WebSphere enterprise facilites, the Open Source web application servers Tomcat and Jetty run well. Use exploded WAR-files to avoid byte code validation startup delays.
JT400 is a set of tools provided by IBM both in standard licensed product and open source forms.
This category has the following 2 subcategories, out of 2 total.