You can write Java™ application programs that use CICS® services and execute under CICS control, but these programs are handled differently from procedural programs written in the traditional CICS languages, such as COBOL and C.
The Java language is designed to be portable and architecture-neutral. The bytecode generated by compilation is portable, but requires a machine-specific interpreter for execution on different platforms. CICS provides this execution environment using a Java Virtual Machine (JVM) that is executing under CICS control.