The Factory Design Pattern is a creational design pattern used to create objects without exposing the object creation logic to the client. Instead of using the new keyword directly, the client relies on a factory method to get the required object.

Factory Design pattern is used when we have a super class with multiple subclass and based on input , we return the one of the subclasses .

Super class in factory pattern can be an interface , abstract class ,or a normal java class .

Example : Computer.java

package om.rkdigital.school.fact;
public abstract class Computer {
	public abstract String getRAM();
	public abstract String getHDD();
	public abstract String getCPU();
}

Pc.java

package om.rkdigital.school.fact;

public class Pc extends Computer{

	private String ram;
	private String hdd;
	private String cpu;
	
	public Pc(String ram, String hdd, String cpu) {
		this.ram=ram;
		this.hdd=hdd;
		this.cpu=cpu;
	}

	@Override
	public String getRAM() {
		// TODO Auto-generated method stub
		return this.ram;
	}

	@Override
	public String getHDD() {
		// TODO Auto-generated method stub
		return this.hdd;
	}

	@Override
	public String getCPU() {
		// TODO Auto-generated method stub
		return this.cpu;
	}	
}

Server.java

package om.rkdigital.school.fact;

public class Server extends Computer{

	private String ram;
	private String hdd;
	private String cpu;
	
	public Server(String ram, String hdd, String cpu) {
		// TODO Auto-generated constructor stub
		this.ram=ram;
		this.hdd=hdd;
		this.cpu=cpu;
	}

	@Override
	public String getRAM() {
		// TODO Auto-generated method stub
		return this.ram;
	}

	@Override
	public String getHDD() {
		// TODO Auto-generated method stub
		return this.hdd;
	}

	@Override
	public String getCPU() {
		// TODO Auto-generated method stub
		return this.cpu;
	}
}

ComputerFactory.java

package om.rkdigital.school.fact;

public class ComputerFactory {
	public static Computer getComputer(String type, String ram, String hdd, String cpu) {
		if("pc".equalsIgnoreCase(type)) {
			return new Pc(ram, hdd, cpu);
		}
		if("server".equalsIgnoreCase(type)) {
			return new Server(ram, hdd, cpu);
		}
		return null;
	}
}

TestFactoryMain.java

package om.rkdigital.school.fact;
public class TestFactoryMain {
	public static void main(String[] args) {
		Computer pc=ComputerFactory.getComputer("pc","2GB","500MB","2.4GB");
		Computer server=ComputerFactory.getComputer("server","2GB","500MB","2.4GB");
		System.out.println(pc.getClass());
		System.out.println(server.getClass());
	}
}