Inheritance

What is Inheritance?
Inheritance allows a new class to be based on an existing class. The news class inherits the members of the class it is based on.  

 A rectangle is a shape 
 A circle is a shapes

How we can use Inheritance?
For our example, we are going to have two subclasses(electric cars, diesel cars) and a parent class(class). Our two subclasses are going to inherit from our parent class. 
First lets code our parent class:
import java.lang.*;

class Cars{

 private String carColor;
 private int maxSpeed;
 private int buildYear;
 private String carModel;

public Cars(String carColor, int maxSpeed, int buildYear, String carModel){
this.carColor = carColor;
this.buildYear = buildYear;
this.carModel = carModel;
this.maxSpeed = maxSpeed;
 }

    public String getCarColor() {
        return carColor;
    }

    public void setCarColor(String carColor) {
        this.carColor = carColor;
    }

    public void setMaxSpeed(int maxSpeed) {
        this.maxSpeed = maxSpeed;
    }

    public void setBuildYear(int buildYear) {
        this.buildYear = buildYear;
    }

    public void setCarModel(String carModel) {
        this.carModel = carModel;
    }

 @Override
    public String toString(){
    return  ("Car color: " + carColor + "\nBuild year: " + buildYear + "\nMax Speed: " + maxSpeed + "-MPH" +  "\nCar Model: " + carModel );
    }

}

Now it is time to code our two subclasses. First let's code our Diesel Cars class:
class DieselCars  extends Cars{ private int milesPerGallon;
public DieselCars(String carColor, int maxSpeed, int buildYear, String carModel, int milesPerGallon) {
        super(carColor, maxSpeed, buildYear, carModel);
        this.milesPerGallon = milesPerGallon;
    }
    public void setMilesPerGallon(int milesPerGallon) {
        this.milesPerGallon = milesPerGallon;
    }
        public String toString(){    return (super.toString()+ "\nMiles Per Gallon: " + milesPerGallon);    }}

Second, let's code our Electric Cars class:
class ElectricCars extends Cars{
private int milesPerCharge;
    public ElectricCars(String carColor, int maxSpeed, int buildYear, String carModel, int milesPerCharge) {
        super(carColor, maxSpeed, buildYear, carModel);
        this.milesPerCharge = milesPerCharge;
    }

    public void setMilesPerCharge(int milesPerCharge) {
        this.milesPerCharge = milesPerCharge;
    }
   
    public String toString(){
    return (super.toString()+ "\nMiles Per Charge: " + milesPerCharge);
    }

}

Time to test our code:
class TestClass{
public static void main(String [] args){
DieselCars myCar = new DieselCars("Red",182,1992,"Ford Mustang", 150);
ElectricCars myECAR = new ElectricCars("Silver", 220, 2017, "Tesla", 250);

System.out.println(myCar.toString());
System.out.println("");
System.out.println(myECAR.toString());

 /*MountainBike mb = new MountainBike(3, 100, 25);
 System.out.println(mb.toString());*/
    }

}

Output:
Car color: Red
Build year: 1992
Max Speed: 182-MPH
Car Model: Ford Mustang
Miles Per Gallon: 150

Car color: Silver
Build year: 2017
Max Speed: 220-MPH
Car Model: Tesla

Miles Per Charge: 250