Cookbooks
Java
Chapter 5. Good Coding Practices
Refactoring

Java:
Refactoring

How to:

Let’s take a simple Java class that’s screaming for refactoring due to its poor organization and lack of clarity.

public class Calculator {
    public int calc(int op1, int op2, String operation) {
        if (operation.equals("add")) {
            return op1 + op2;
        } else if (operation.equals("subtract")) {
            return op1 - op2;
        } // Other operations...
    }
}

After refactoring, we have:

public class Calculator {
    public int add(int operand1, int operand2) {
        return operand1 + operand2;
    }

    public int subtract(int operand1, int operand2) {
        return operand1 - operand2;
    }

    // Other operations...
}

By refactoring, we’ve improved the method names and parameters for readability and removed the need for a conditional branch within a single method. Each operation now clearly states its purpose.

Deep Dive:

Refactoring has its roots in the Smalltalk community, with its emphasis on code readability and object-oriented design, but it really took off in the Java world in the late ’90s and early ’00s, particularly after the publication of Martin Fowler’s seminal book, “Refactoring: Improving the Design of Existing Code.”

There are alternatives to refactoring, like rewriting code from scratch. However, refactoring is often preferred because it involves incremental changes that do not disrupt the functionality of the application.

Implementation details when refactoring in Java (or any programming language) revolve around understanding code smells—indicators of deeper issues in the code. Some smells include long methods, large classes, duplicate code, and excessive use of primitives. By applying refactoring patterns such as Extract Method, Move Method, or Replace Temp with Query, developers can systematically address these smells while ensuring the code remains functional at all times.

Automated tools, like IntelliJ IDEA’s refactoring support, or plugins for Eclipse, can aid the process by automating refactorings such as renaming variables, methods, and classes, extracting methods or variables, and moving methods or classes to different packages or namespaces.

See Also:

Each of these resources provides either a foundation for understanding the principles of refactoring or tools that can be leveraged to put these principles into practice.

Organizing code into functions