Factory Design Pattern Example in JAVA

If we have a super class and n sub-classes, and based on data provided, we have to return the object of one of the sub-classes, we use a factory pattern.

Here is one super class and n subclasses, yeah factory of classes :)

When to use a Factory Pattern?
The Factory patterns can be used in following cases:
1. When a class does not know which class of objects it must create.
2. A class specifies its sub-classes to specify which objects to create.
3. In programmer’s language (very raw form), you can use factory pattern where you have to create an object of any one of sub-classes depending on the data provided.

We also use this pattern where a family of classes implements one interface.

Let’s 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. and if the sex is Female (F), it displays message saying Hello Ms .

public class Person {
      // name string
public String name;
// gender : M or F
private String gender;

public String getName() {
return name;
}

public String getGender() {
return gender;
}
}// End of class

This is a simple class Person having methods for name and gender. Now, we will have two sub-classes, Male and Female which will print the welcome message on the screen.

public class Male extends Person {
      public Male(String fullName) {
System.out.println("Hello Mr. "+fullName);
}
}// End of class

And also the female class

public class Female extends Person {
      public Female(String fullNname) {
System.out.println("Hello Ms. "+fullNname);
}
}// End of class

Now, we have to create a client, or a SalutationFactory which will return the welcome message depending on the data provided.

public class SalutationFactory {
      public static void main(String args[]) {
SalutationFactory factory = new SalutationFactory();
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;
}
}// End of class

On running this program like

JAVA James

it will return

Hello Mr James