Replace Magic Number with Symbolic Constant

In software development, a “magic number” is a direct usage of a number in the code. These numbers can sometimes be confusing and can lead to difficulties when trying to understand the purpose of the number. In order to improve the readability and maintainability of the code, it’s often a good idea to replace these magic numbers with symbolic constants. This is a common refactoring technique known as “Replace Magic Number with Symbolic Constant”.

When Should it be Applied?

This refactoring technique should be applied when you have a number in your code that has a specific meaning but is not immediately clear from the context. Magic numbers can make the code harder to understand and maintain, as the meaning of the number is not immediately clear. By replacing the magic number with a symbolic constant, you can make the code more readable and easier to understand.

It’s also beneficial to apply this refactoring when the same magic number is used in multiple places. If the value of the number ever needs to change, you would have to find and update every instance of that number. By using a symbolic constant, you only need to change the value in one place.

Example in Java

Let’s consider an example where we have a magic number in our code. Suppose we have a method that calculates the area of a circle:

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

In this code, 3.14159 is a magic number. It’s the mathematical constant pi, which is the ratio of a circle’s circumference to its diameter. But if someone else reads this code, they might not immediately recognize this.

We can refactor this code by replacing the magic number with a symbolic constant:

public class Circle {
    private static final double PI = 3.14159;

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

Now, instead of using the magic number 3.14159, we use the symbolic constant PI. This makes the code more readable and maintainable. If we ever need to change the value of pi (for example, to add more precision), we only need to change it in one place.

In conclusion, the “Replace Magic Number with Symbolic Constant” refactoring technique is a simple but effective way to improve the readability and maintainability of your code. By replacing magic numbers with symbolic constants, you can make your code easier to understand and change.