My understanding of Factory Pattern

Going by definition Factory pattern is a creational design pattern used in software development to encapsulate the processes involved in the creation of objects.

In simple terms we can say that factory pattern is a good choice when we need to create object depending on some parameter at runtime.

Let’s say if we have a super class and sub-classes, and based on data provided (any parameter), we have to return the object of one of the sub-classes, then factory pattern is the ideal choice.

Lets take a simple example to understand its working..

Suppose we have an application which stores Customer details like name and sex etc. Depending on sex the application will create either a male or a female object and accordingly print a hello message.

public class Customer {

public String name;

//gender : M or F

private String gender;

public String getName() {

return name;

}

public String getGender() {

return gender;

}

}

Customer class is having methods for name and gender. And the sub classes will print hello message as shown below.

public class Male extends Customer {

public Male(String name) {

System.out.println("Hello Mr. "+name);

}

}

public class Female extends Customer {

public Female(String name) {

System.out.println("Hello Ms. "+name);

}

}

Now create a client, called CustomerFactory which will return Male or Female object depending on the data provided

public class CustomerFactory {

public static void main(String args[]) {

CustomerFactory factory = new CustomerFactory();

factory.getCustomer(args[0], args[1]);

}

public Customer getCustomer(String name, String gender) {

if (gender.equals("M"))

return new Male(name);

else if(gender.equals("F"))

return new Female(name);

else

return null;

}

}

On compiling and running this client program..

Java CustomerFactory Sarah F

The output is: “Hello Ms. Sarah”.

Now let’s summarize when to use Factory Pattern

· When a class does not know which class of objects it must create.

· When we want to encapsulate the process of creating the objects.

· When we have to create an object of any one of sub-classes depending on the data provided.

So now its time to create your own factories as you wish J