There are three methods to evaluate networked systems during the design phase: by means of simulation, a practical testbed, and mathematical analysis. In this paper, we propose the jUDPWrapper, which enables to access the OMNeT++/INET UDP functionality from Java using the Java Extensions for OMNeT++. The jUDPWrapper provides a socket-based API corresponding to the standard API defined in the java.net package. Consequently, it enables to develop application layer simulation models in Java and here- after easily derive a Java prototype implementation. Therefore, the jUDPWrapper eases the evaluation of Java UDP applications using both simulation and practical testbed. We evaluate the jUDPWrapper using two distinct versions of OMNeT++/INET, provide the Java Extensions for OMNeT++ 5.4, and for the first time quantify the execution time of Java models versus C++ models. C++ models are approx. twice as fast as Java models in long simulation runs, if the release mode is used.