Duplicated code leads to errors. Say you have two classes Sedan and Truck. They’re different types, but they share a few properties and methods, like SpeedUp() and SlowDown(). If one of those members (say it’s SpeedUp()) has to change, then we would have to change the code in every location where SpeedUp() is defined.

In this case it’s two classes, but in other programs it may be many more! There are two reasons we don’t want to make the same change on code across multiple files:

• It’s a waste of time
• More importantly, it is a big risk for making mistakes

In this lesson you’ll learn about a solution to this problem: inheritance. With inheritance, you can define one superclass that contains the shared members (like SpeedUp() and SlowDown()). All classes that need those members can inherit them from the superclass.