What is refactoring?

Refactoring is the process of improving the internal structure of existing code without changing its external behavior. The goal is to make the code more readable, maintainable, and extendable by eliminating duplication, improving naming, simplifying logic, and restructuring.

An example of simple refactoring in Java:

// Before refactoring
public double calculateArea(double radius) {
    return 3.14159 * radius * radius;
}

// After refactoring using a constant
public static final double PI = 3.14159;

public double calculateArea(double radius) {
    return PI * radius * radius;
}

Refactoring helps maintain high code quality and facilitates further development.