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The introduction to object-oriented concepts in the lesson titledObject-oriented Programming Conceptsused a bicycle class as an example, with racing bikes, mountain bikes, and tandem bikes as subclasses. Here is sample code for a possible implementation of aBicycle class, to give you an overview of a class declaration. Subsequent sections of this lesson will back up and explain class declarations step by step. For the moment, don't concern yourself with the details.
public class Bicycle { //the Bicycle class has //threefields public int cadence; public int gear; public int speed; //the Bicycle class has //oneconstructor public Bicycle(int startCadence, int startSpeed, int startGear) { gear = startGear; cadence = startCadence; speed = startSpeed; } //the Bicycle class has //fourmethods public void setCadence(int newValue) { cadence = newValue; } public void setGear(int newValue) { gear = newValue; } public void applyBrake(int decrement) { speed -= decrement; } public void speedUp(int increment) { speed += increment; } }A class declaration for aMountainBike class that is a subclass ofBicycle might look like this:
public class MountainBike extends Bicycle { //the MountainBike subclass has //onefield public int seatHeight; //the MountainBike subclass has //oneconstructor public MountainBike(int startHeight, int startCadence, int startSpeed, int startGear) { super(startCadence, startSpeed, startGear); seatHeight = startHeight; } //the MountainBike subclass has //onemethod public void setHeight(int newValue) { seatHeight = newValue; } }MountainBike inherits all the fields and methods ofBicycle and adds the fieldseatHeight and a method to set it (mountain bikes have seats that can be moved up and down as the terrain demands).
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