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LESSON 187 OF 348 · OBJECT-ORIENTED PROGRAMMING

Method Overriding in Scala in Scala

Lesson

TL ; DR:

When a child class defines a method with the same name as the parent's, the child's version overrides the parent's. Different objects can give the same method name different behavior.


class Dog {
    def bark() { println("Woof!"); }
}
class Puppy extends Dog {
    @Override
    def bark() { println("Yip!"); }
}


Full lesson:

You've seen that a child class inherits the parent's methods. Overriding is what happens when the child wants to change one of those inherited methods.

Why override?

Subclasses are usually special cases of the parent. A Puppy is a Dog, but it sounds different — "Yip!" instead of "Woof!". Instead of inventing a new method name, you redefine bark() on the Puppy. Callers don't need to know which subclass they're holding — they just call bark() and the right version runs.

How it works in each language

  • C# — the parent method must be marked virtual, the child marks its replacement override. The compiler enforces this pairing.
  • Java — every non-final method is virtual by default; the @Override annotation is optional but tells the compiler to verify the signature matches.
  • Python — defining a method with the same name in the child class replaces the parent's. No keyword required.
  • Scala — same as Python: define the method again on the child class and it wins.
  • C++ — the parent method must be virtual; override on the child is optional but compiler-checked.

Your task

The Dog class already defines bark. Inside the Puppy subclass, override bark so it prints "Yip! I am " followed by the puppy's name. The harness creates a Puppy named "Buddy" and calls bark() on it.

Expected output:

Yip! I am Buddy
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    Method Overriding in Scala

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