14. Method Overriding

Summary

In this video, the concept of method overriding in object-oriented programming (OOP) is explained. Method overriding allows a child class to redefine a method already present in its parent class. The video demonstrates how this technique works using a `Vehicle` class with a `sound` method, and shows how a derived `Car` class can override the method to produce a different sound. Key points covered include the importance of maintaining method signatures and using the `@Override` annotation to avoid errors. The tutorial emphasizes how method overriding helps customize behavior in derived classes.

Takeaways

• 😀 Method overriding allows a child class to redefine a method from its parent class.
• 😀 Overriding a method in a derived class means that the method in the parent class can no longer be directly accessed unless explicitly referenced.
• 😀 The method signature (name, return type, etc.) must be the same when overriding a method in the child class.
• 😀 In the example, the `Vehicle` class has a `sound()` method that outputs a default sound (e.g., 'ngeng ngeng').
• 😀 The `Car` class overrides the `sound()` method to change the sound to 'member member'.
• 😀 It’s important to maintain the same method signature when overriding, so the child class method has the same name and structure as the parent class.
• 😀 Annotations like `@Override` can be added to make it clear that a method is overriding a parent class method.
• 😀 If a method is overridden in a subclass, the new behavior takes precedence for objects of that subclass.
• 😀 The overridden method in the `Car` class produces a different sound compared to the default sound in the `Vehicle` class.
• 😀 The `Motorcycle` class, which does not override the `sound()` method, continues to use the original 'ngeng ngeng' sound.
• 😀 Method overriding allows for more specific behavior in subclasses, making object-oriented programming more flexible and customizable.

Q & A

What is method overriding in object-oriented programming?

Method overriding is the ability to redefine a method in a child class that already exists in its parent class, allowing the child class to provide its specific implementation of the method.

How does method overriding affect the parent class method?

When a method is overridden in the child class, the parent class method is no longer directly accessible when an object of the child class is created, unless explicitly called using the 'super' keyword.

Why is it important to ensure the method declaration is the same when overriding?

It's important because the method name and signature (parameters and return type) must match in the parent and child classes for the override to be valid and work as intended.

What was the example given in the video to explain method overriding?

The example involved a 'Vehicle' class with a 'sound' method. The method was overridden in a 'Car' class to change the vehicle sound from 'ngeng ngeng' to a 'bucket' sound.

What is the purpose of using the @Override annotation?

The @Override annotation is used to indicate that a method is overriding a method in its parent class. It helps catch errors if the method signature does not correctly match the one in the parent class.

Can a child class change the functionality of a parent class method completely?

Yes, by overriding the method, the child class can change its functionality to suit its specific needs, replacing the behavior of the parent class method.

What will happen if a child class does not override a method from its parent class?

If the child class does not override the method, it will inherit the parent class’s version of the method and use it as is.

What happens when you test the overridden method in the 'Car' and 'Motorcycle' classes?

When testing the overridden method in the 'Car' class, it produces the new sound (e.g., 'bucket'). In the 'Motorcycle' class, which does not override the method, the original sound ('ngeng ngeng') is produced.

How do you differentiate between a parent class method and a child class overridden method?

You can differentiate them by using the @Override annotation in the child class, which indicates that the method is an override of the parent class method.

What would happen if the method name in the child class doesn't match the parent class method?

If the method name does not match exactly, the child class will not override the method, and a compilation error will occur.