CASE STUDIES OF ACCESSIBILITY EXCESSIVENESS ANALYSIS FOR JAVA PROGRAMS

Dotri Quoc

Inoue Laboratory

RESEARCH PROBLEM(1)ACCESS MODIFIER IN JAVA

public int[] A ; protected int c ; …..public void sort(){…}(default) int binarySearch(int value){…}private void process(){…}

CLASS1

Access Modifier

field declaration

method declaration

RESEARCH PROBLEM(2)

Access Modifier of fields/methods in Java : control the access of other classes　 to that field/method.

Access Modifier

Same Class

Package Subclass Any Class

Public OK OK OK OK

Protected OK OK OK -

Default OK OK - -

Private OK - - -

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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

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EXAMPLE OF BAD ACCESS MODIFIER DECLARATION

Current program Main job

Other objects

Initialization

Public method A Public method B

Class X

Directly invoke B

Invoke

Future modification

OK

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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

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Access Modifier

Same Class

Package Subclass Any Class

Public OK OK OK OK

Protected OK OK OK -

Default OK OK - -

Private OK - - -

Declaration

Actual use

AE

AE : ACCESSIBILITY EXCESSIVENESS(2/2)

Acquirement of AE for each field/method AE causes bug in latter development and

maintenance phase

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AE analysis tool : ModiChecker

APPROACH TO AE ANALYSIS(1)AE MAP

Actual Usage

Declaration Public Protected Default Private Unused

Public ok-pub0

pub1 pub2 pub3 pub4

Protected- ok-pro0 pro1 pro2 pro3

Default - - ok-def0 def1 def2

Private - - - ok-pri0 pri1

Syntax Error

No Discrepanc

y

AE IdAE Id of Excessive

fields/methods

Unused

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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

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Static source code Analysis is required

Employing MASU

MASU - http://sourceforge.net/projects/masu/

ARCHITECTURE OF MODICHECKER

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Extraction of access modifier

declaration

Extraction of method/field

usage

ModiChecker

Source Code Analyzer

AST Database

MASU

Detection of declaration excessiveness

Input

Report of AE Id for each method/field

Source Code

Required Library(.jar

files)

OVERVIEW OF EXPERIMENT(1/2) Objectives of experiment

Validation of our approach Quantitative analysis of AE Id in some software systemsReasons for excessive/unused fields/methods

(found by interviewing developers)1. Reason 1 : Set for future use2. Reason 2 : Created by other program(automatic code

generators or refactoring tools…) or accessed by other programs(Java bean)

3. Reason 3 : Carelessness and immaturity　 Target Software

Industrial Software(341 Java files/ 64455 LOC)11

EXPERIMENT RESULT - FIELDS

Actual Usage

Declaration Public Protected Default Private Unused

Public 207 0 59 936 33

Protected- 0 9 18 0

Default - - 4 5 2

Private - - - 1123 5

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EXPERIMENT RESULT - METHODS

Actual Usage

Declaration Public Protected Default Private Unused

Public 816 14 23 190 1005

Protected- 13 36 48 9

Default - - 0 3 0

Private - - - 488 4

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EXPERIMENT RESULT

Excessive fields : 1027 Excessive methods : 512 Unused methods : 1018 Unused fields: 40

5 fields named serialVersionUIDIntentionally set for future use : 8Actually unused : 28 (5 fields contain

potential bug)

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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

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CONCLUSION AND FUTURE WORK

ConclusionAnalysis method named AE for each

field/methodModiChecker : report AE of each

field/methodExperiment on some software　 systems

Future workModiChecker for other Java systems and

other programming language system(C# , C++…)

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THANK YOU FOR YOUR ATTENTION

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