1. ModiChecker : Accessibility Excessiveness Analysis Tool for Java Program
Dotri Quoc†, Kazuo Kobori†, Norihiro Yoshida*, Yoshiki Higo† , Katsuro Inoue†
† : Osaka University, Japan * : Nara Institute of Science and Technology , Japan

2. AE Analysis Tool : ModiChecker Experiment and Discussion
Outline
Introduction
AE Analysis Tool : ModiChecker
Experiment and Discussion
Conclusion and future work
Delete the symbol of MASU….
JSSST11
2019/5/19

3. Encapsulation in Java Programming
One characteristic of object oriented programming
Object’s code and data is hidden from other objects
Interface encapsulates objects’ code and data
Good Encapsulation : choosing appropriate access modifier for fields/methods
Bad habit of Access Modifier setting : public or default(no explicit declaration）
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4. Example of Bad Access Modifier Declaration- Binary Search
int[] A ;
…..
public void sort(){ … }
public int binarySearch(int value){
//Find index of value in array
public void process(){
int x;
// set value of x from some where ….
this.sort() ;
int index = this.binarySearch(x) ;
// other operation with index ;
CLASS1
Set value for array object.A
Sorting Array　A in an order
public void process{
CLASS1 object = new CLASS1() ; …
//searching a value in array without sorting
int index = object.binarySearch(10) ; }
CLASS2
Searching
Private
Initialization
sort
binarySearch
Calling
Order
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5. AE : Accessibility Excessiveness(1/2)
AE : Discrepancy between declared access modifier and actual usage
An AE could caused unwilling access to method/field
AE could be used as an indicator of immaturity of developer
Properties of AE
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6. 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
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7. AE Analysis Tool : ModiChecker Experiment and Discussion
Outline
Introduction
AE Analysis Tool : ModiChecker
Experiment and Discussion
Conclusion and future work
JSSST11
2019/5/19

8. AE Analysis Tool : ModiChecker
AE analysis for Java Program
Report excessiveness for each field/method
Requirement for implementation :
Access Modifiers declaration and actual usage of field/method from other objects
AE Map : define all cases of AE
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9. Approach to AE Analysis 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 -
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10. Approach to AE Analysis-AE Map (1/2)
Java Access Modifier
Public : can be accessed by all classes
Protected: can be only accessed by classes in the same package and subclasses
Default :can be only accessed by classes in the same package.
No explicit Access Modifier is declared
Private: can be only accessed from inside of owner class
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11. Approach to AE Analysis-AE Map (2/2)
Accessibility Excessive Map
AE Id
AE Id of Excessive fields/methods
Actual Usage
Declaration
Public
Protected
Default
Private
ok-pub0
pub1
pub2
pub3 -
ok-pro0
pro1
pro2
ok-def0
def1
ok-pri0
Syntax Error
No Discrepancy
Explain access range of java access modifier
Change x to –
Change default to package without None
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12. Architecture of ModiChecker
Extraction of access modifier declaration
Extraction of method/field usage
ModiChecker
Source Code Analyzer
AST Database
MASU
Detection of declaration excessiveness
Source Code
Required Library(.jar files)
Input
Report of AE Id for each method/field
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13. Special Cases for ModiChecker
No report for methods of Abstract classes and Interfaces
Method overriding an other method case
overriding method must have an access modifier equal or more permissive level to the access modifier of the overridden method
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14. Example of Method Overriding Method Case
public method C()
Class A
Class B
Access modifier of C must be public
Even if method B.C was only accessed from inside class B, ModiChecker still reported method B.C the AE Id of pub0
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15. AE Analysis Tool : ModiChecker Experiment and Discussion Conclusion
Outline
Introduction
AE Analysis Tool : ModiChecker
Experiment and Discussion
Conclusion
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2019/5/19

16. Overview of Experiment(1/2)
Objectives of experiment
Validation of our approach
Quantitative analysis of AE Id in open source code
Reasons for excessiveness
Reason 1 : Set for future use　
Reason 2 : Created by other program(automatic code generators or refactoring tools…)　
Reason 3 : Carelessness and immaturity　
Change number in latter pages
State the experiment process
Object of experiment : validation of our approach, Quantitative analyses of AE ID in open source
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17. Overview of Experiment(2/2)
Target Software
Ant (1141 files, LOC)
jEdit 4.4.1(546 files, LOC)
MASU(519 files, LOC)
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18. Result of Ant(1/2) Ratio of each AE Id
18.9%
35.5%
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19. Result of Ant(2/2) Excessive fields Excessive methods
Total number : 611(18.9%)
Set for future use : unknown
Created by other program : 0
Carelessness and immaturity : unknown
Excessive methods
Total number : 1520(35.5%)
Ratio of excessive methods > ratio of excessive fields
Encapsulation : Make fields private and provide public getter/setter to access fields
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20. Result of jEdit(1/2) Ratio of each AE Id
24.1%
30.4%
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21. Result of jEdit(2/2) Excessive fields Total number : 604(24.1%)
Set for future use : unknown
Created by other program : 0
Carelessness and immaturity : unknown
Excessive methods
Total number : 981(30.4%)
Ratio of excessive methods > ratio of excessive fields
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22. Result of MASU(1/2) Ratio of each AE Id
35.7%
14.3%
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23. Result of MASU(2/2) Excessive fields Total number : 280(35.7%)
Set for future use : 20
Created by other program(automatic code generator) : 255
Carelessness and immaturity : 5
Excessive methods
Total number : 253(14.3%)
Set for future use : 181
Created by other program(automatic code generator) : 6
Carelessness and immaturity : 66
Ratio of excessive fields > ratio of excessive methods
Caused by fields created by automatic code generator
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24. Discussion(1/3) Validation of ModiChecker output
Change all of the excessive access modifier by hand
Modified programs were compiled and executed without any error
Conclusion for excessiveness
Number for reason
State the reason first , then give the solution
English grammar
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25. Discussion(2/3) Solution for excessiveness
Reason 1 : Excessiveness set for future use
requirement of tool which let developer select fields/methods to change access modifier
Reason 2 : Excessiveness created by other programs
Using ModiChecker after using refactoring tools or automatic code generating tools
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26. Discussion(3/3) Proposal of new quality metrics
AE index for each AE id and metrics value is total of AE index of all methods/fields
Set value for each field/method based on the number of potential unexpected access. Metrics value is total of those values.
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27. AE Analysis Tool : ModiChecker Experiment and Discussion
Outline
Introduction
AE Analysis Tool : ModiChecker
Experiment and Discussion
Conclusion and future work
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2019/5/19

28. Conclusion Analysis method named AE for each field/method
ModiChecker : find excessiveness and report AE of each field/method
Experiment on some open softwares
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29. Future works
Apply ModiChecker for other Java systems and other programming language system(C# , C++…)
AE analysis result and other program quality indicators such as bug frequency
Number of AE index
Number of Bug
C# : public internal protected private
C++ : Private, Protected and Public.
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30. THANK YOU FOR YOUR ATTENTION
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