REFACTORING

Movie Rental Refactoring (Inspired by Martin Fowler)

This project is a Java console application that demonstrates how to refactor messy, procedural code into clean, object-oriented design, inspired by Martin Fowler's book "Refactoring: Improving the Design of Existing Code."

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Project Description

The app simulates a simple video rental store system, where:

• A customer can rent different types of movies (Regular, Children’s, New Releases)
• The program calculates the total rental cost
• It also awards frequent renter points
• A clean text statement is generated

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Technologies Used

• Java (standard libraries)
• Console-based UI

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What Was Refactored

I started from a long, procedural statement() method in the Customer class. It was:

• Calculating charges
• Building strings
• Containing switch logic

This broke the Single Responsibility Principle.

Refactoring Changes Made:

Change	Why
Extracted getCharge() and getFrequentRenterPoints() to Rental.java	Logic belongs to the object it uses (Rental)
Replaced Vector and Enumeration with List and modern for-each	Cleaner, safer, and modern Java style
Broke down statement() into smaller methods (header(), lineForRental(), footer())	Easier to read, test, and extend
Used StringBuilder and String.format()	Better performance and formatting

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Testing the Application

This project includes a full JUnit 5 (Jupiter) test suite.
The tests cover all the core components of the application to ensure correctness and easy future maintenance.

Test Coverage

Class	Test Class	Coverage Description
Customer	CustomerTest	Tests statement generation and frequent renter points
Rental	RentalTest	Tests charge calculation and bonus point logic
Movie	MovieTest	Tests title and price code getter/setter methods

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Running the Tests (Manual CLI Method)

Make sure you have JUnit Console Standalone downloaded in your lib/ folder.

1. Compile everything:

**javac -cp ".:lib/junit-platform-console-standalone-1.12.2.jar" -d bin src/.java test/.java **

2. Run the tests:

java -jar lib/junit-platform-console-standalone-1.12.2.jar --class-path bin --scan-class-path

3.Output

├─ JUnit Jupiter ✔ │ ├─ MovieTest ✔ │ │ └─ testMovieGettersAndSetters() ✔ │ ├─ CustomerTest ✔ │ │ ├─ testFrequentRenterPointsForNewReleaseOneDay() ✔ │ │ └─ testStatementWithMultipleRentals() ✔ │ └─ RentalTest ✔ │ ├─ testFrequentRenterPointsStandard() ✔ │ ├─ testGetChargeForRegularMovie() ✔ │ ├─ testGetChargeForChildrensMovie() ✔ │ ├─ testGetChargeForNewRelease() ✔ │ └─ testFrequentRenterPointsBonus() ✔