BEST SITE FOR WEB DEVELOPERS
Java programming language. Lessons for beginners

Ua

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);
  }
}
Try it Yourself »

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)
Try it Yourself »