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Java Inheritance

Java Inheritance (Subclass and Superclass)

In Java, it is possible to inherit assets and methods from one class to another. We combine the concept of an inheritance into two categories:

• subclass(child) - a category that benefits from another class
• superclass(parent) - the inherited category

To get an asset from the class, use an extends keyword.

In the example below, the Car category (sub-category) inherits the attributes and methods from the Vehicle class (top category):

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?

Set the brand attribute on Vehicle as a protected access controller. If set to private, the Car class will not be able to access it.

Why And When To Use "Inheritance"?

- Useful for code reuse: re-use the attributes and methods of the existing class when creating a new class.

Tip: Also look at the next chapter, Polymorphism, which uses inherited methods to perform various functions.

The final Keyword

If you do not want other classes to inherit the classroom, 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:

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