Recently, Java has been educated in many universities and professional schools due to reliability, portability, and scalability. However, because of its limited time in Java programming courses, coding rules are rarely educated. As a result, codes made by students become far from readable codes. In this paper, we propose a coding rule learning function using static code analyzers in Java Programming Learning Assistant System (JPLAS), targeting students who have accomplished the grammar learning and are going to write practical codes for final projects. Coding rules for this function consist of naming rules, coding styles, and potential problems. We evaluate the improvement of readability in four codes refined by this function and the usability of this function through the questionnaires completed by five students. In future studies, we expect that this function will be employed in Java programming courses.