CPSC 210
D3: Refactoring
Slides designed by Felix Grund, based on Paul Carter’s slides
Learning Goals
- To improve the design of an existing code base through refactoring
- To improve coupling by abstracting duplicated code into methods
- To improve cohesion by splitting up classes
Cohesion (SRP): High = Good
Coupling: Low = Good
Refactoring
- When we refactor code...
- we do not change the functionality of the code
- we want to improve the structure of the code
- We want to improve code structure by...
- reducing repetitive code
- reducing coupling
- increasing cohesion (SRP)
Improving code structure without changing functionality
Pod Activity (Do in Groups of 3-5)
When refactoring, why can't we just update/alter the functionality at the same time?
Refactoring
Improving code structure without changing functionality
Fully working code base with tests!
Tests keep passing!
Real-World Example
...from a tool that you all know and love...
Lecture Ticket
- Duplication between the two methods!
- We want to refactor and extract a helper method
- What lines to pull out from each method?
- What to pass into the method when called from each method?
- What is the return type of the helper method?
public class LittleClass {
public int doThingOne() {
int numTimes = 6;
int multiplier = 5;
numTimes += 1;
for (int i = 0; i < numTimes; i++) {
System.out.println(multiplier * i);
}
return numTimes;
}
public void doThingTwo() {
int occurrences = 3;
int timeser = 10;
System.out.println("Doing thing two");
for (int i = 0; i < occurrences; i++) {
System.out.println(timeser * i);
}
System.out.println("Doing thing two");
}
}Lecture Lab
Run the code · adapt the test suite · add new test suites · code from the UI package should be moved out
Clone · re-organize using the diagram · start with Zoo, Animal and Stall · finally work on Receptionist
