You Look so Different: Finding Structural Clones and Subclones in Java Source Code

Code reuse and copying is a widespread practice in software development. Detecting code clones, i.e., identical or similar fragments of code, is thus an important task with many applications, ranging from code search to bug finding and malware detection. In this paper, we propose a new approach to detect code clones in source code. Instead of analyzing the code tokens or syntax, our technique is based upon control flow analysis and dominator trees. In this way, the technique not only detects exact and syntactically similar near-miss code clones but also two new types of clones, which we characterize as structural code clones and subclones. For implementation and evaluation, we have developed the tool StoneDetector, which finds code clones in Java source code. StoneDetector performs competitive with the state of the art as measured on the BigCloneBench benchmark and finds more structural clones and subclones.