Specify the JVP

To execute, a UDR written in Java™ code must run in a JVP. The JVP is a predefined virtual-processor class that contains a Java™ virtual machine to interpret Java™ byte codes.

Use the following syntax to specify that a UDR executes in the JVP class: 
WITH (class='jvp')

By default, most UDRs run in the CPU VP, which does not contain a Java™ virtual machine. However, a UDR written in Java™ code runs on a JVP by default. Therefore, the CLASS routine modifier is optional when you register a UDR written in Java™ code. To improve readability of your SQL statements, include the CLASS routine modifier when you register a UDR.

For example: 
-- Specifying the JVP
CREATE PROCEDURE showusers()
   WITH (class='jvp')
   EXTERNAL NAME 'thisjar:admin.showusers()'
   LANGUAGE java;