Error Message :
Any java.lang.NoClassDefFoundError

for example:
java.lang.NoClassDefFoundError: com.uc4.communication.requests.XMLRequest

There is a missing file in the documentation on how to install the Java CallAPI.
Since Version 11 of the Java CallAPI in addition to uccall3.jar you need to import uc4.jar as well, otherwise you will receive a java.lang.NoClassDefFoundError depending on which method you try to call in the java code.
 

Cause type:
Defect
Root Cause: The jar file structure has been optimized to make it smaller and easier to maintain.

Release: AUTWAB99000-11.0-Automic Workload Automation-Base Edition
Component:

This field was added on 30/03/2017. This article has not been updated yet. Refer to the "Description" or "Workaround" sections for solution information.

Fix Status: Released

Fix Version(s):
Documentation Guides of Automation.Engine 12.0.0 - already available
Documentation Guides of Automation.Engine 11.1.4 - already available
Documentation Guides of Automation.Engine 11.2.3 - already available

Workaround :
N/A