Making the car class abstract

Introduzione alla programmazione orientata agli oggetti in Java

Sani Yusuf

Lead Software Engineering Content Developer

Explaining abstract class

The phrase Car only exists as a placeholder
We still need to know more like what type of car it is

Toyota

Mercedes

Food analogy for abstract class

You never ask for just food at a restaurant
You always specify what type of food you want to eat
- bread
- pasta
- rice

Bread

Pasta

Rice

Understanding abstract classes

Abstract classes exist to hold features for inheriting classes
Abstract classes cannot have object instances created
Abstract classes generally do not have code implementation

Car abstract class


  // Car abstract class
  abstract class Car {    
    // abstract drive method
     abstract void drive(); // No Code Implementation 

  }

Abstract methods

Abstract method have no implementation
The class that inherits, must implement abstract methods


   // Car abstract class
  abstract class Car {    
    // abstract drive method
     abstract void drive(); // No Code  
                            // implementation
  }


  // Toyota class 
  class Toyota extends Car {  
     void drive(){
      // Toyota drive() implementation
    }           
  }

  // Porsche class
  class Porsche extends Car {  
     void drive(){
      // Porsche drive() implementation
    }           
  }

Creating concrete methods

Concrete methods are the methods with code implementation
Subclasses do not need to implement concrete methods


  // abstract Car class
  abstract class Car {
    private int topSpeed;

    // Concrete method with implementation
    public getTopSpeed(){
         return this.topSpeed;
    }

    abstract void drive(); 
    // No Code Implementation        
  }

Let's practice!

Introduzione alla programmazione orientata agli oggetti in Java