Factory Pattern

Factory pattern comes from creational design pattern category.main objective of this pattern is to instantiate an object and Factory pattern interface is responsible for creating objects but the sub-classes desides which class to instantiate.


Im going to start with a simple example.Suppose an application asks for entering the name and sex of a person. If the sex is Male (M), it displays welcome message saying Hello Mr. <Name> and if the sex is Female (F), it displays message saying Hello Ms <Name>.


First Im going to create a Person class..

public class Person {

    public String name;
    public String gender;

    public String getName() {
        return name;
    }

    public String getGender() {
        return gender;
    }
}

we have 2 sub classes which will print welcome messages

public class Male extends Person {

    public Male(String name) {
        System.out.println("Mr. " + name);
    }
}

public class Female extends Person {

    public Female(String name) {
        System.out.println("Ms." + name);
    }
}

Im going to create a WelcomeMessageFactory class which will return welcome messages according to the input data..

public class WelcomeMessageFactory{

    private static void main(String args[]) {
        WelcomeMessageFactory factory = new WelcomeMessageFactory();
        factory.getPerson(args[0], args[1]);
    }

    public Person getPerson(String name, String gender) {
        if (gender.equals("M")) {
            return new Male(name);
        } else if (gender.equals("F")) {
            return new Female(name);
        } else
            return null;
    }
}

This class accepts two arguments from the system at runtime and prints the names and sex..


after compiling run the program with 
java Madura M


out put is 
Mr. Madura