1 Design Patterns

King Fahd University of Petroleum and Engineering

ICS Department

SWE 436

082

Design Patterns Term Project

Team members:

Mohannad Shahat 244698 Feras AlTurigi 244638 Hosain Alhasmy 244126

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TABLE OF CONTENT

LIST OF FIGURES ......................................................................................................................................... 3

1. Introduction .................................................................................................................................. 4

1.1. Reference Material ....................................................................................................................... 4

2. Tools .............................................................................................................................................. 4

2.1. PINOT ............................................................................................................................................ 4

2.1.1. Configuration ................................................................................................................................ 6

2.2. ExamDiff Pro ................................................................................................................................. 6

2.2.1. Configuration ................................................................................................................................ 7

2.3. Understand ................................................................................................................................... 8

2.3.1. Configuration ................................................................................................................................ 8

3. Analysis ......................................................................................................................................... 8

3.1. jEdit 4.0 ......................................................................................................................................... 9

3.1.1. LCOM and CBO Analysis .............................................................................................................. 11

3.2. jEdit 4.2 ....................................................................................................................................... 13

3.2.1. LCOM and CBO Analysis .............................................................................................................. 15

3.3. Conclusion ................................................................................................................................... 16

4. AppenDIX .................................................................................................................................... 17

4.1. Appendix I: jEdit 4.0 .................................................................................................................... 17

4.2. Appendix II: jEdit 4.2 ................................................................................................................... 17

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LIST OF FIGURES

Figure 1 Comparison Option in ExamDiff Pro ................................................................................................. 7 Figure 2 Filter Option in ExamDiff Pro ............................................................................................................ 8 Figure 3 ........................................................................................................................................................... 9 Figure 4 ......................................................................................................................................................... 10 Figure 5 ......................................................................................................................................................... 10 Figure 6 ......................................................................................................................................................... 11 Figure 7 ......................................................................................................................................................... 11 Figure 8 ......................................................................................................................................................... 12 Figure 9 ......................................................................................................................................................... 12 Figure 10 ....................................................................................................................................................... 13 Figure 11 ....................................................................................................................................................... 14 Figure 12 ....................................................................................................................................................... 14 Figure 13 ....................................................................................................................................................... 15 Figure 14 ....................................................................................................................................................... 15 Figure 15 ....................................................................................................................................................... 16 Figure 16 ....................................................................................................................................................... 16

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1. INTRODUCTION

In this project we took a closer look at an open-source system “jEdit” examining the

design patterns at the source code level. This report will show our findings and how

can the use of design patterns affect the stability of a system. It will compare three

versions of jEdit and show how the number of design patterns changed from one

release to another and how stable each version from the other ones. The analysis in

this report is limited to the accuracy of PINOT tool that automate the process of

finding design patterns in Java source code.

1.1. Reference Material

1. jEdit4.0.txt (PINOT output)

2. jEdit4.2.txt (PINOT output)

2. TOOLS

2.1. PINOT

PINOT is a tool that detects the occurrence of most Gang of Four design patterns

(GoF). It takes as an input a java file or paths to java files, and generates a report

of the design patterns found in the system with some statistics. Here is part of an

output from running PINOT on jEdit4.0: ./pinot -classpath /Users/sophto_92/Downloads/2009-05-16/pinot/lib/rt.jar @/Users/sophto_92/Desktop/SWE436\ Project/jEdit/jEdit4.0/FilesList.txt --------- Original GoF Patterns ---------- Singleton Pattern ReflectManager is a Singleton class rfm is the Singleton instance getReflectManager creates and returns rfm File location: /Users/sophto_92/Desktop/SWE436 Project/jEdit/jEdit4.0/bsh/ReflectManager.java Chain of Responsibility Pattern Primitive is a Chain of Responsibility Handler class toString is a handle operation value of type Object propogates the request File Location: /Users/sophto_92/Desktop/SWE436 Project/jEdit/jEdit4.0/bsh/Primitive.java

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Chain of Responsibility Pattern REToken is a Chain of Responsibility Handler class dumpAll is a handle operation next of type REToken propogates the request File Location: /Users/sophto_92/Desktop/SWE436 Project/jEdit/jEdit4.0/gnu/regexp/REToken.java ---------- Chain of Responsibility Pattern RE is a Chain of Responsibility Handler class setUncle is a handle operation lastToken of type REToken propogates the request File Location: /Users/sophto_92/Desktop/SWE436 Project/jEdit/jEdit4.0/gnu/regexp/RE.java Chain of Responsibility Pattern RE is a Chain of Responsibility Handler class match is a handle operation firstToken of type REToken propogates the request File Location: /Users/sophto_92/Desktop/SWE436 Project/jEdit/jEdit4.0/gnu/regexp/RE.java ------------- Decorator Pattern RETokenRepeated is a Decorator class getMinimumLength is a decorate operation token of type REToken is the Decoratee class File Location: /Users/sophto_92/Desktop/SWE436 Project/jEdit/jEdit4.0/gnu/regexp/RETokenRepeated.java ……… ------------------------------------------ Pattern Instance Statistics: Creational Patterns ============================== Abstract Factory 3 Factory Method 4 Singleton 1 ------------------------------ Structural Patterns ============================== Adapter 6 Bridge 1 Composite 5 Decorator 2 Facade 20 Flyweight 15 Proxy 13 ------------------------------ Behavioral Patterns ==============================

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Chain of Responsibility 3 Mediator 64 Observer 2 State 0 Strategy 7 Template Method 0 Visitor 0 ------------------------------ Number of classes processed: 239 Number of files processed: 312 Size of DelegationTable: 5161 Size of concrete class nodes: 175 Size of undirected invocation edges: 256 nMediatorFacadeDual/nMediator = 4/64 nImmutable/nFlyweight = 9/15 nFlyweightGoFVersion = 0

2.1.1. Configuration

To run PINOT on your machine you first need to have a Unix-based system

running. Then do the following steps: 1. After extracting the downloaded file. 2. > cd pinot 3. > ./configure --prefix=PREFIX --enable-debug 4. > make 5. > make install 6. The executable file pinot is located in PREFIX/bin (e.g: /Users/bin/) 7. To run PINOT you need to include rt.jar in the classpath :

./pinot -classpath /Users/admin/pinot/lib/rt.jar /Users/admin/Desktop/jEdit/RE.java

When you want to supply to PINOT a collection of java files, you can put

them in a text file then execute this command: ./pinot -classpath /Users/admin/pinot/lib/rt.jar @/Users/admin/Desktop/jEdit/jEdit.txt

For more information about the tool visit: http://www.cs.ucdavis.edu/~shini/research/pinot/

2.2. ExamDiff Pro

ExamDiff Pro is a powerful yet intuitive and easy to use visual file and directory

comparison tool. It features unique functionality that distinguishes ExamDiff Pro

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from other comparison programs. ExamDiff Pro offers a much more efficient and

user-friendly way to compare files and folders.

2.2.1. Configuration

In ExamDiff Pro, we included in the comparison only the java files and

excluded many things like comments and so on, See the pictures below.

After you configured the tool, run a “Full Comparison” to get accurate result

of what has changed and what has not changed.

Figure 1 Comparison Option in ExamDiff Pro

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Figure 2 Filter Option in ExamDiff Pro

For more information about ExamDiff Pro visit: http://www.prestosoft.com/edp_examdiffpro.asp

2.3. Understand

Understand helps programmers to quickly comprehend measure, maintain and

document their source code. For many, especially those working on large,

multiple MSLOC projects, it has become an indispensable tool.

2.3.1. Configuration

After installing Understand, you only need to give as an input the root

directory to the source code. Then the tool will generate the report in an

HTML and RTF formats.

For more information about the tool visit: http://www.scitools.com/products/understand/

3. ANALYSIS

In this section we will examine the matrices collected from Understand and

ExamDiff against the stability (changeability) of Object Oriented Design Patterns.

The matrices are collected from jEdit 4.0 and jEdit 4.2 source codes. As a result jEdit

4.0 is compared against jEdit 4.2 and jEdit 4.2 is compared against jEdit 4.3. This

analysis focus on how stable to use design pattern and uses comparison techniques

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between the stability of the classes participate in design patterns and classes that do

not participate in design pattern. Two main matrices we used of the classes

relatedness which are CBO Count of Coupling Between Objects and LCOM

Percent Lack of Cohesion of Methods. This analysis accuracy relays on the Pinot

accuracy of detecting design patterns as mentioned in the introduction.

3.1. jEdit 4.0

In the statistics collected, Figure3, from jEdit 4.0 shows that 40% of the system

classes are participating in design patterns whereas 60% of the system classes are

not participating in design patterns. This will lead to the comparison between the

two types of classes against changes in the jEdit 4.2.

Figure 3

As appears in the statistics, Figure4, Figure5, the changes of the participate

classes is 65% to the overall participate classes while the changes in not

participate classes is 72% of the overall not participate classes. Since the classes

that participate in patterns has less percentage than the classes that are not

participate in patterns, we can conclude that the classes participate in patterns are

tend to be more stable from jEdit 4.0 to jEdit 4.2 than the classes that are not

participate in patterns.

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Figure 4

Figure 5

We need to analyze which pattern (or type of pattern) is tending to be more stable

than the others. The statistics, Figure6, Figure7, shows that Factory, Façade and

Strategy have the highest percentage of change over the other patterns (Even

though singleton has percentage of 100% change but it occurs once in the

system). Flyweight is tend to be the most stable pattern in the jEdit 4.0 since it has

only 28% change with the number of occurrences 15 (Even though Decorator and

Bridge has percentage of 100% not change but it occurs only once and twice

respectively in the system). Creational patterns seem to have the highest

percentage of change among the other type of patterns with percentage of 83%.

This percentage is affected by the factory pattern since it has 80% percentage of

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change and number of occurrence 4. The Structural pattern has the minimum

percentage of changes with 56%.

Figure 6

Figure 7

3.1.1. LCOM and CBO Analysis

LCOM and CBO should be low as much as possible to achieve better design.

However, Structural design pattern tends to have the highest LCOM and

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CBO among the other types of patterns since the bridge pattern has the

highest percentage in both LCOM and CBO which are 95% and 24%

respectively. This concludes that the system classes relays on the Structural

pattern more than the other types. Taking in the consideration the Structural

pattern percentage of change, we do not expect that the overall classes will

change significantly. See Figure8 and Figure9 below.

Figure 8

Figure 9

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3.2. jEdit 4.2

The overall number of classes has increased in the jEdit 4.2. In the statistics,

Figure10, collected from jEdit 4.2 shows that 38% of the system classes are

participate in design patterns whereas 62% of the system classes are not

participate in design patterns. This will lead to the comparison between the two

types of classes against changes in the jEdit 4.3.

Figure 10

As appears in the statistics, Figure11, Figure12, the changes of the participate

classes is 24% to the overall participate classes while the changes in not

participate classes is 59% of the overall not participate classes. As it appears

adding more patterns drops the percentage of change significantly. Since the

classes that participate in patterns has less percentage than the classes that are not

participate in patterns, we can conclude that the classes participate in patterns are

tend to be more stable from jEdit 4.2 to jEdit 4.3 than the classes that are not

participate in patterns.

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Figure 11

Figure 12

We need to analyze which pattern (or type of pattern) is tending to be more stable

than the others. The statistics, Figure13, Figure14, shows that Proxy and

Flyweight have the highest percentage of change over the other patterns. The

other patterns are much more stable in jEdit 4.2 since the number of added

patterns has increased significantly.

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Figure 13

Figure 14

3.2.1. LCOM and CBO Analysis

Behavioral design pattern tends to have the highest LCOM and CBO among

the other types of patterns since the Visitor pattern has the highest

percentage in both LCOM and CBO which are 89% and 31% respectively.

This concludes that the system classes relays on the Behavioral pattern more

than the other types. See Figure15 and Figure16 below.

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Figure 15

Figure 16

3.3. Conclusion

Design patterns occurrence increased with each release.

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Even though design patterns affect the performance and it is hard to evaluate

stability, but we think it increases the stability of the system.

LCOM and CBO should be taken in the consideration.

The trend from one release to another in jEdit (4.0 4.2 4.3) is that the

classes participating are less changeable than other classes and their occurrence

is increasing. This made us conclude that using design pattern is very good in

solving common problem in the design.

Finally, developer should spend more time investigating the applicability of a

certain design pattern to apply it only in the correct place. It also should be

commented what type of patterns are used and where for later maintenance and

evaluation studies.

4. APPENDIX

4.1. Appendix I: jEdit 4.0

4.2. Appendix II: jEdit 4.2