Static Factory Method and New Keyword in Java

Factory pattern is a design pattern (creational pattern) which is used to create multiple objects based on the data we provide. In it we create an object abstracting the process of creation.

Example

Below given is the example implementation of the factory pattern. Here, we have an interface with name Employee and 3 classes: Student, Lecturer, NonTeachingStaff, implementing it. We have created a factory class (EmployeeFactory) with a method named getEmployee(). This method accepts a String value and returns an object of one of the classes, based on the given String value.

import java.util.Scanner;
interface Person{
   void dsplay();
}
class Student implements Person{
   public void dsplay() {
      System.out.println("This is display method of the Student class");
   }
}
class Lecturer implements Person{
   public void dsplay() {
      System.out.println("This is display method of the Lecturer class");
   }
}
class NonTeachingStaff implements Person{
   public void dsplay() {
      System.out.println("This is display method of the NonTeachingStaff class");
   }
}
class PersonFactory{
   public Person getPerson(String empType) {
      if(empType == null){
         return null;
      }
      if(empType.equalsIgnoreCase("student")){
         return new Student();
      } else if(empType.equalsIgnoreCase("lecturer")){
         return new Lecturer();
      } else if(empType.equalsIgnoreCase("non teaching staff")){
         return new NonTeachingStaff();
      }
      return null;
   }
}
public class FactoryPattern {
   public static void main(String args[]) {
      Scanner sc = new Scanner(System.in);
      System.out.println("Enter the type of the object you want: (student, lecturer, non teaching staff)");
      String type = sc.next();
      PersonFactory obj = new PersonFactory();
      Person emp = obj.getPerson(type);
      emp.dsplay();
   }
}

Output

Enter the type of the object you want: (student, lecturer, non teaching staff)
lecturer
This is display method of the Lecturer class

Static factory method

Though it is said that there are five ways to create an object in Java namely −

• Using the new keyword.
• Using the Factory method.
• Using cloning.
• Using Class.forName().
• Using object deserialization.

The only way to create an object in Java is using the new keyword all other ways are abstractions to it. Intact all these methods internally use the new keyword.

Example

import java.util.Scanner;
interface Employee{
   void dsplay();
}
class Student implements Employee{
   public void dsplay() {
      System.out.println("This is display method of the Student class");
   }
}
class Lecturer implements Employee{
   public void dsplay() {
      System.out.println("This is display method of the Lecturer class");
   }
}
class NonTeachingStaff implements Employee{
   public void dsplay() {
      System.out.println("This is display method of the NonTeachingStaff class");
   }
}
class EmployeeFactory{
   public static Employee getEmployee(String empType) {
      if(empType == null){
         return null;
      }
      if(empType.equalsIgnoreCase("student")){
         return new Student();
      } else if(empType.equalsIgnoreCase("lecturer")){
         return new Lecturer();
      } else if(empType.equalsIgnoreCase("non teaching staff")){
         return new NonTeachingStaff();
      }
      return null;
   }
}
public class FactoryPattern {
   public static void main(String args[]) {
      Scanner sc = new Scanner(System.in);
      System.out.println("Enter the type of the object you want: (student, lecturer, non teaching staff)");
      String type = sc.next();
      EmployeeFactory obj = new EmployeeFactory();
      Employee emp = EmployeeFactory.getEmployee(type);
      emp.dsplay();
   }
}

Output

Enter the type of the object you want: (student, lecturer, non teaching staff)
lecturer
This is display method of the Lecturer class