Abstract: A plagiarism detection approach to detect both Java source code and byte code was proposed. The proposed method compares Java source files or class files by multiple similarity measures developed to represent the syntax structures and semantic features of the programs. An efficient plagiarism detection tool using the proposed technique was developed to analyze plagiarism behavior of Java source code or class code. Statistical analysis and several graphical visualizations aid in the interpretation of analysis results. An experimental comparison with a typical commercial source code plagiarism detection tool as well as a case study by applying the tool to plagiarism detection with a set of manually modified programs were conducted. Experiment results show that the tool is more efficient and the proposed technique can recognize both exact copy and approximate copy, including those most of the types of source code transformations in program plagiarism behavior.