An application that runs in an IMS Java dependent region must start with the main method of a class. A COBOL class definition with a main factory method meets this requirement; therefore, you can use it as the first routine of a mixed COBOL and Java IMS application.
Enterprise COBOL generates a Java class with a main method that the IMS Java dependent region can find, instantiate, and invoke in the same way that the region does for the main method of an IMS Java IMSApplication subclass. Although you can code the entire application in COBOL, you would probably build this type of application to call a Java routine. When COBOL runtime support runs within the JVM of an IMS Java dependent region, it automatically finds and uses this JVM to invoke methods on Java classes.
However, the COBOL application is not derived from the IMSApplication class, and it should not use the IMS Java classes for processing messages or synchronizing transactions. Instead, it should use DL/I calls in COBOL for processing messages (GU and GN) and synchronizing transactions (CHKP).