Java Basics Using Qt Jambi Tutorial

Classes

We've already seen classes from previous examples like class Vehicle. In object-oriented programming (OOP), we always create the most common or generalized class.

Ex.

public class Vehicle{

}

We created the class as Vehicle and from that, we put methods that is common to all vehicles.

Ex.

public class Vehicle{

public void accelerate(){

}

public void decelerate(){

}

public void start(){

}

public void stop(){

}

public void turnDirection(){

}

}

Then we create a “sub-class” called “Car”:

public class Car extends Vehicle{

public void turnOnRadio(){

}

public void turnOnWiper(){

}

}

And, also inheriting from Vehicle class we create:

public class Bicycle extends Vehicle{

public void adjustMirror(){

}

public void soundRinger(){

}

}

The Car and Bicycle are called sub-classes and Vehicle is the super class. We call this “inheritance.”

Then we can access the super class methods in our code.

Ex.

public static void main(String[] args){

Car car1 = new Car();

car1.start(); //since we inherited the methods in super class Vehicle, we can call its methods.

car1.accelerate();

car1.turnOnRadio(); //we can also use Car's own methods.

car1.stop();

Note: We can also use Vehicle's properties such as variables, constructors by using the super keyword, and even the super class' overriding methods.

Ex.

public class Vehicle{

public void start(){

System.out.println(“Start your engines”);

}

}

public class Car extends Vehicle(){

public void start(){

super.start();

}

}

Example of executing constructors in super class:

public class Vehicle{

public Vehicle(){

}

}

public class Car extends Vehicle{

public Car(){

super();

}

}

It can also pass in arguments:

public Car(int wheels, int doors){

super(wheels,doors)

}

to be continued...