Java programming language belongs to a group of object-oriented programming languages and is one of the most used languages for building applications or programs. It is constantly worked on new features and refinement of language, so it is interesting to see the difference in performances between individual versions. For testing different versions of Java in this paper were used applications with microservice architecture. Such architectural style divides system into a collection of smaller services that are mutually independent, loosely coupled and organized according to their tasks and purpose. For this reason, applications with such architecture are very sustainable and suitable for testing. System efficiency and performances affect and allocate memory that system has available for applications. Java has embedded automatic memory management and a garbage collector that works in the background and releases memory by deleting unused objects. The main part of memory is called a heap memory. Heap memory is used to store the actual objects whose references are located on the stack. Each JVM process has its own heap memory that is divided by number of threads within the process. Java VisualVM was used to display heap memory status throughout tests. This tool displays graphically the exploitation of heap memory, processor usage, number of loaded classes and number of active threads at specific moment. Docker was used to run the RAP component and its container, that ran RAP component, was also monitored to see its memory consumption. Efficiency and performances of specific system were tested by sending HTTP requests that were simulated automatically using the Gatling tool. Different number of users was simulated to see system behavior and performances at higher loads. Testing was carried out on the same computer where applications were also running. Testing has been successful and the test results are satisfactory. There is a remarkable improvement in performance with newer versions of Java, which predicts that each new version will be better and more desirable to use.