Factory Design Pattern

/*package whatever //do not write package name here */
// without factory

import java.io.*;

// Library classes
abstract class Vehicle {
    public abstract void printVehicle();
}

class TwoWheeler extends Vehicle {
    public void printVehicle() {
        System.out.println("I am two wheeler");
    }
}

class FourWheeler extends Vehicle {
    public void printVehicle() {
        System.out.println("I am four wheeler");
    }
}

// Client (or user) class
class Client {
    private Vehicle pVehicle;

    public Client(int type) {
        if (type == 1) {
            pVehicle = new TwoWheeler();
        } else if (type == 2) {
            pVehicle = new FourWheeler();
        } else {
            pVehicle = null;
        }
    }

    public void cleanup() {
        if (pVehicle != null) {
            pVehicle = null;
        }
    }

    public Vehicle getVehicle() {
        return pVehicle;
    }
}

// Driver program
public class GFG {
    public static void main(String[] args) {
        Client pClient = new Client(1);
        Vehicle pVehicle = pClient.getVehicle();
        if (pVehicle != null) {
            pVehicle.printVehicle();
        }
        pClient.cleanup();
    }
}

/****************************  With Factory *********************************************/
// Library classes
abstract class Vehicle {
    public abstract void printVehicle();
}

class TwoWheeler extends Vehicle {
    public void printVehicle() {
        System.out.println("I am two wheeler");
    }
}

class FourWheeler extends Vehicle {
    public void printVehicle() {
        System.out.println("I am four wheeler");
    }
}

// Factory Interface
interface VehicleFactory {
    Vehicle createVehicle();
}

// Concrete Factory for TwoWheeler
class TwoWheelerFactory implements VehicleFactory {
    public Vehicle createVehicle() {
        return new TwoWheeler();
    }
}

// Concrete Factory for FourWheeler
class FourWheelerFactory implements VehicleFactory {
    public Vehicle createVehicle() {
        return new FourWheeler();
    }
}

// Client class
class Client {
    private Vehicle pVehicle;

    public Client(VehicleFactory factory) {
        pVehicle = factory.createVehicle();
    }

    public Vehicle getVehicle() {
        return pVehicle;
    }
}

// Driver program
public class GFG {
    public static void main(String[] args) {
        VehicleFactory twoWheelerFactory = new TwoWheelerFactory();
        Client twoWheelerClient = new Client(twoWheelerFactory);
        Vehicle twoWheeler = twoWheelerClient.getVehicle();
        twoWheeler.printVehicle();

        VehicleFactory fourWheelerFactory = new FourWheelerFactory();
        Client fourWheelerClient = new Client(fourWheelerFactory);
        Vehicle fourWheeler = fourWheelerClient.getVehicle();
        fourWheeler.printVehicle();
    }
}