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  • Java
  • Java Inheritance

Java Inheritance (Subclass and Superclass)

In Java, it is possible to inherit attributes and methods from one class to another. We group the "inheritance concept" into two categories:

  • subclass (child) - the class that inherits from another class
  • superclass (parent) - the class being inherited from

To inherit from a class, use the extends keyword.

In the example below, the Car class (subclass) inherits the attributes and methods from the Vehicle class (superclass):

Example

class Vehicle {

  protected String brand = "Ford";        // Vehicle attribute

  public void honk() {                    // Vehicle method

    System.out.println("Tuut, tuut!");

  }

}

 

class Car extends Vehicle {

  private String modelName = "Mustang";    // Car attribute

  public static void main(String[] args) {

 

    // Create a myCar object

    Car myCar = new Car();

 

    // Call the honk() method (from the Vehicle class) on the myCar object

    myCar.honk();

 

    // Display the value of the brand attribute (from the Vehicle class) and the value of the modelName from the Car class

    System.out.println(myCar.brand + " " + myCar.modelName);

  }

}

 

Did you notice the protected modifier in Vehicle?

We set the brand attribute in Vehicle to a protected access modifier. If it was set to private, the Car class would not be able to access it.

Why And When To Use "Inheritance"?

- It is useful for code reusability: reuse attributes and methods of an existing class when you create a new class.

Tip: Also take a look at the next chapter, Polymorphism, which uses inherited methods to perform different tasks.

The final Keyword

If you don't want other classes to inherit from a class, use the final keyword:

If you try to access a final class, Java will generate an error:

final class Vehicle {

  ...

}

 

class Car extends Vehicle {

  ...

}

The output will be something like this:

Main.java:9: error: cannot inherit from final Vehicle
class Main extends Vehicle {
                  ^
1 error)

 

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