Program $5$: In the below example of inheritance, class Bicycle is a base class, class MountainBike is a derived class that extends the Bicycle class and class Test is a driver class to run the program.

class Bicycle $\{$

$//$ the Bicycle class has two fields

public int gear;

public int speed;

$//$ the Bicycle class has one constructor

public Bicycle$($int gear, int speed$)$

$\{$

this.gear $=$ gear;

this.speed $=$ speed;

$\}$

$//$ the Bicycle class has three methods

public void applyBrake$($int decrement$)$

$\{$

speed $-=$ decrement;

$\}$

public void speedUp$($int increment$)$

$\{$

speed $+=$ increment;

$\}$

$//$ toString$()$ method to print info of Bicycle

public String toString$()$

$\{$

return $("$No of gears are $"+$ gear $+"$

$"$

$+$ "speed of bicycle is $"+$ speed$)$;

$\}$

$\}$

$//$ derived class

class MountainBike extends Bicycle $\{$

$//$ the MountainBike subclass adds one more field

public int seatHeight;

$//$ the MountainBike subclass has one constructor

public MountainBike$($int gear, int speed,

int startHeight$)$

$\{$

$//$ invoking base$-$class$($Bicycle$)$ constructor

super$($gear$,$ speed$)$;

seatHeight $=$ startHeight;

$\}$

$//$ the MountainBike subclass adds one more method

public void setHeight$($int newValue$)$

$\{$

seatHeight $=$ newValue;

$\}$

$\}$

$//$ driver class

public class Test $\{$

public static void main$($String args$[])$

$\{$

MountainBike mb $=$ new MountainBike$(3,100,25)$;

System.out.println$($mb$.$toString$())$;

$\}$

$\}$

Note: We will add this later to the above program

$////$ overriding toString$()$ method of Bicycle to print more info

@Override public String toString$()$

$\{$

return $($super$.$toString$()+"$

seat height is $"$

$+$ seatHeight$)$;

$\}$