Code Smell of the year

Magic number


When you change your perspective on the screen from the development to the refactoring view, it often happens that various numbers appear.

Numbers that change become variables. Numbers are okay, as long as they aren’t changed they should be converted to constants.

Well, numbers are often referred to as “magic numbers”. If you are reading code, it is not really clear why is there a (magic) number like 10 or else.

Let’s take a look at following code snippet: 

public class Vehicle {

    void automaticTransmission(int rpm){
        if(rpm > 4000){
            changeGearUp();
        }
    }

    ...
}


4000 is speculatively. Change it to a constant in the code and make it more readable. 

public class Vehicle {

    private final int MAXIMUM_RPM = 4000; 

    void automaticTransmission(int rpm){
        if(rpm > MAXIMUM_RPM){
            changeGearUp();
        }
    }
    ...
}


This is step one of the first part of the Refactoring kickstart beginner series. Here is step 2.