The computing education community has shown a long-time interest in how to analyze the Object Oriented (OO) source code developed by students to provide them with useful formative tips. However, it is essential for instructors to understand the student’s difficulties. This allows to provide students precise feedback of their most frequent mistakes and helps instructors to shape, design and drive the course in an effective way. This paper proposes and evaluates an approach allowing to analyze student’s source code and to give feedback to the student about their mistakes. The approach is implemented through a cloud-based integrated development environment (IDE) allowing to understand how students use Java and its language constructs. The approach is based on the analysis of the most common violations of the Object-Oriented paradigm in the student source code. Moreover, the environment supports the automatic generation of reports about student’s mistakes and misconceptions that can be used by instructors to improve the course design. The paper discusses the results of an experiment performed in a class of a Programming II course to investigate the effects of the provided reports in terms of coding ability (concerning the correctness and the quality of the produced source code).