Case Studies of Accessibility Excessiveness Analysis for Java Programs

1. Case Studies of Accessibility Excessiveness Analysis for Java Programs DotriQuoc Inoue Laboratory

2. Research Problem(1)Access Modifier in Java CLASS1 publicint[] A ; • protectedint c ; ….. • public void sort() { … } • (default)intbinarySearch(int value) { … } private void process(){ … } field declaration Access Modifier method declaration

3. Research Problem(2) • Access Modifier of fields/methods in Java : control the access of other classesto that field/method.

4. Research Problem(3) • In Java, inexperienced/careless developers often set all of the access modifier public or default(no declaration) • The fields/methods which should be hidden are not hidden • Bugs in latter development/maintenance phase

5. Example of bad access modifier Declaration Class X Public method B Public method A Current program OK Initialization Main job Invoke Other objects Future modification Directly invoke B

6. AE : Accessibility Excessiveness(1/2) • AE : Discrepancy between declared access modifier and actual usage • An AE could cause unwilling access to method/field • AE could be used as an indicator of immaturity of developer Declaration AE Actual use

7. AE : Accessibility Excessiveness(2/2) • Acquirement of AE for each field/method • AE causes bug in latter development and maintenance phase AE analysis tool : ModiChecker

8. Approach to AE Analysis(1)AE MAP Unused AE Id AE Id of Excessive fields/methods Syntax Error No Discrepancy

9. Approach to AE Analysis(2) Static Source Code Analysis • Requirement • Information of each field/method’s access modifier declaration • Actual Usage of each field/method • MASU : Platform for Metrics measurement but is useful as a Java program analysis framework Static source code Analysis is required Employing MASU MASU - http://sourceforge.net/projects/masu/

10. Architecture of ModiChecker ModiChecker Input MASU Source Code Analyzer AST Database Source Code Extraction of access modifier declaration Extraction of method/field usage Required Library(.jar files) Detection of declaration excessiveness Report of AE Id for each method/field

11. Overview of Experiment(1/2) • Objectives of experiment • Validation of our approach • Quantitative analysis of AE Id in some software systems • Reasons for excessive/unused fields/methods (found by interviewing developers) • Reason 1 : Set for future use • Reason 2 : Created by other program(automatic code generators or refactoring tools…) or accessed by other programs(Java bean) • Reason 3 : Carelessness and immaturity • Target Software • Industrial Software(341 Java files/ 64455 LOC)

12. EXPERIMENT RESULT - FIELDS

13. EXPERIMENT RESULT - METHODS

14. EXPERIMENT RESULT • Excessive fields : 1027 • Excessive methods : 512 • Unused methods : 1018 • Unused fields: 40 • 5 fields named serialVersionUID • Intentionally set for future use : 8 • Actually unused : 28 (5 fields contain potential bug)

15. Discussion • Validation of ModiChecker output • Changed all of the excessive access modifier and deleted some unused fields/methods • Modified programs were compiled and executed without any error • Developer should look for the detailed result and make decision to change/delete the unused/excessive fields/methods

16. Conclusion AND FUTURE WORK • Conclusion • Analysis method named AE for each field/method • ModiChecker : report AE of each field/method • Experiment on some softwaresystems • Future work • ModiCheckerfor other Java systems and other programming language system(C# , C++…)

17. Thank you for your attention