Interactive Computer Science Tutoring

Learn programming concepts interactively

What Is a Class?

Learn how classes serve as blueprints for creating objects

Understanding Classes

A class is like a blueprint or template. Just as bicycle manufacturers use the same blueprint to create many bicycles, programmers use classes to create many objects of the same type.

Each bicycle object created from the Bicycle class has its own state (cadence, speed, gear) and can perform the same behaviors (change gear, speed up, brake).

Bicycle Objects (Instances)2 instances

Each bicycle is an instance of the Bicycle class with its own state

Mountain Bike

Selected

Cadence:0 RPM

Speed:0 mph

Gear:1

Road Bike

Cadence:0 RPM

Speed:0 mph

Gear:1

Bicycle Methods

Change Cadence

Change Gear

Speed Control

Create New Bicycle

Instantiate a new object from the Bicycle class

Reset Demo

Java Code

Live Java representation with highlighted changes

// Bicycle class - the blueprint for bicycle objects
public class Bicycle {
// Instance variables (state)
    int cadence = 0;
    int speed = 0;
    int gear = 1;
// Methods (behavior)
     void changeCadence(int newValue) {
        cadence = newValue;
    }
     void changeGear(int newValue) {
        gear = newValue;
    }
     void speedUp(int increment) {
        speed = speed + increment;
    }
     void applyBrakes(int decrement) {
        speed = speed - decrement;
    }
     void printStates() {
        System.out.println("cadence:" + cadence + " speed:" + speed + " gear:" + gear);
    }
}
// Demo class showing how to create and use Bicycle objects
public class BicycleDemo {
    public static void main(String[] args) {
// Create bicycle objects (instances of the class)
        Bicycle bike1 = new Bicycle();
// Mountain Bike
        Bicycle bike2 = new Bicycle();
// Road Bike
// Current state of bicycle objects:
// Mountain Bike (bike1):
//   cadence: 0, speed: 0, gear: 1
// Road Bike (bike2):
//   cadence: 0, speed: 0, gear: 1
// Example method calls:
// bike1.changeCadence(50);
// bike1.speedUp(10);
// bike1.changeGear(2);
// bike1.printStates();
    }
}

History0/5

Recent method calls and object operations

No operations yet

Start by adding or modifying elements