CSC/ECE 517 Fall 2009/wiki1a 9 mk

Research in Refactoring Tools

Refactoring

Refactoring is the process of modifying existing source codebase in a structured and incremental way while preserving its external behavior. This process preserves the functionality of the program without introducing new bugs. Refactoring also promotes reuse of the existing codebase for other purposes thus increasing code reusability.

Overview

The fundamental work is primarily focused on the definitions and mechanism of refactoring, and proving their correctness. Refactoring means that the behaviour/functionality of the program does not change and therefore any program which meets its specifications before refactoring will continue to meet those specifications even afterwards. Refactoring can be done on any codebase and it is a general set of operations. Hence it comes with preconditions which specifies under what circumstances refactoring can be performed, also with the conformation that the dependency graphs are unchanged even after the refactoring is performed.

Current Automated Refactoring Tools

Features of some Refactoring Tools

Refactoring can be grouped into three broad categories.

1. Changing the name and physical organization of code, including renaming fields, variables, classes, and interfaces, and moving packages and classes.

2. Changing the logical organization of code at the class level, including turning anonymous classes into nested classes, turning nested classes into top-level classes, creating interfaces from concrete classes, and moving methods or fields from a class to a subclass or superclass.

3. Changing the code within a class, including turning local variables into class fields, turning selected code in a method into a separate method, and generating getter and setter methods for fields.

Given below is an example of Refactoring,

 void printValues() {
   		double averageAge = 0;
 		double totalSalary = 0;
 		for (int i = 0; i < people.length; i++) {
 				averageAge += people[i].age;
 				totalSalary += people[i].salary;
 		}
 		averageAge = averageAge / people.length;
 		System.out.println(averageAge);
 		System.out.println(totalSalary);
 	}
 
 The refactored code:
 
 void printValues() {
 		System.out.println(averageAge());
 		System.out.println(totalSalary());
 	}
 
 	private double averageAge() {
 		double result = 0;
 		for (int i = 0; i < people.length; i++) {
 				result += people[i].age;
 		}
 		return result / people.length;
 	}
 
 	private double totalSalary() {
 		double result = 0;
 		for (int i = 0; i < people.length; i++) {
 				result += people[i].salary;
 		}
 		return result;
 	}
 

Improvement for Current Refactoring Tools

Tools that help the programmers with selection should:

1.Be lightweight. Users can normally select code quickly and efficiently, and any tool to assist selection should not add overhead to slow down the common case.

2.Help the programmer overcome unfamiliar or unusual code formatting.

3.Allow the programmer to select code in a manner specific to the task they are performing. For example, while bracket matching can be helpful, bracketed statements are not the only meaningful program construct that a programmer needs to select.

Conclusion

Refactoring is an important part of software development and refactoring tools are critical to making refactoring fast and behavior preserving. In this paper, I have presented three new tools that help programmers avoid selection errors and understand violations of refactoring preconditions. Through a user study, I have demonstrated that these tools exhibit several qualities that improve the experience of refactoring, help programmers correctly identify problems with a proposed refactoring, and increase speed of the refactoring process. I hope that these qualities will be adopted by new refactoring tools, make tools more usable and thus more used, and eventually contribute to the production of more reliable, on-time software.