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Test-Driven Development in Java

Simplifying Maintenance with SRP

Explore how applying the Single Responsibility Principle (SRP) to Java code helps you refactor complex classes into simpler, more maintainable parts. Learn to distribute responsibilities across specialized classes, reduce code duplication, and organize tests for clearer, localized fault detection. This lesson shows you how SRP leads to stable abstractions and easier code evolution.

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Refactoring for single responsibility

To see the value of applying SRP, let’s consider a piece of code that doesn’t use it. The following code snippet has a list of shapes that all get drawn when we call the draw() method:

Java
import java.util.ArrayList;
import java.util.List;
public class main {
    public static void main(String[] args) {
        Shapes shapes = new Shapes();
        shapes.add(new TextBox("Hello, World!"));
        shapes.add(new Rectangle(5, 3));
        Graphics graphics = new Graphics();
        shapes.draw(graphics);
    }
}

We can see that this code has four responsibilities, as follows:

  • Managing the list of shapes with the add() method

  • Drawing all the shapes in the list with the draw() method

  • Knowing every type of shape in the switch statement

  • Has implementation details for drawing each shape type in the case statement

If we want ...