how to use sub class of extended class code example

Example 1: java how to extend a class

class A{
  //some code
}
class B extends A{ //keyword used is extends
  //some code
}

Example 2: public class extends java super

public MountainBike(int startHeight, 
                    int startCadence,
                    int startSpeed,
                    int startGear) {
    super(startCadence, startSpeed, startGear);
    seatHeight = startHeight;
}