Live Refactoring Session: Getting rid of dirty code

Marcus Biel

A typical refactoring situation: Untested legacy code, written in Java 5, 14 years ago. Without tests we cannot touch the code, but without touching and understanding the code we cannot write tests. Chicken-and-egg problem! What to do?

In this live hacking I will refactor a small Sudoku Brute Force Solver. The code is anything but bad, but its age shows. In short sections we want to give the legacy code a rejuvenating treatment. In doing this, I want to introduce you to my personal approach when refactoring untested legacy code.

Among many other things, we will cover:
- Code readability
- Comments
- General OO
- Encapsulation
- Coupling
- Cohesion
- Immutable Classes
- Modern IO
- Java 8 Streams

I recommend that you familiarize yourself with the Sudoku rules and check the original code beforehand:
https://github.com/fzoli/Sudoku/blob/master/src/java/sudoku/chan/SudokuSolver.java
https://github.com/fzoli/Sudoku/blob/master/src/java/sudoku/chan/Grid.java