Factory Method Design Pattern in Java by Vikram Gupta Javarevisited

Table Of Content

• Factory Design Pattern With Java
• Important Topics for the Factory Method in Java Design Patterns
• Factory Design Pattern Examples in JDK
• Types of Structural Design Patterns in Java:
• Factory Design Pattern Super Class
• Factory Method Design Pattern Use Case Example:
• Types of Behavioral Design Pattern in Java:

Understanding when and how to apply the factory design pattern effectively can enhance your skills as a software developer and improve your applications. The template method pattern is a behavioral design pattern and is used to create a method stub and to defer some of the steps of implementation to the subclasses. The template method defines the steps to execute an algorithm, and it can provide a default implementation that might be common for all or some of the subclasses. The abstract factory pattern is similar to the factory pattern and is a factory of factories.

Factory Design Pattern With Java

If you are ordering a car, then based on your requirements or specifications, the factory will create the appropriate car and then deliver that car to you. According to Gang of Four (GOF), the Factory Design Pattern states that A factory is an object which is used for creating other objects. In technical terms, we can say that a factory is a class with a method. That method will create and return different types of objects based on the input parameter, it received. Proxy Method is a structural design pattern, it provide to create a substitute for an object, which can act as an intermediary or control access to the real object.

Important Topics for the Factory Method in Java Design Patterns

So I think the first advantage in the section should be what I said above at least. In this article, I am going to discuss the Factory Design Pattern in Java with Real-Time Examples. Please read our previous article where we give a brief introduction to the Creational Design Pattern. The Factory Design Pattern is one of the most frequently used design patterns in real-time applications. The Factory Design Pattern falls under the Creational Design Patterns Category. Template Method is a Behavioral Design Pattern, it defines the skeleton of an algorithm in a method but lets subclasses alter some steps of that algorithm without changing its structure.

Factory Design Pattern Examples in JDK

This logic will stay hidden from the end user, as we'll be specifying which implementation we want through the argument passed to the SpaceshipFactory method used for instantiation. Instead of hard-coding object creation into the createSpaceship() method with new operators, we'll create a Spaceship interface and implement it through a couple of different concrete classes. If the factory is a class - the subclasses can use existing implementation or optionally override factory methods. Each concrete factory is responsible for creating an instance of a specific concrete product.

Step 5

Building a car requires many steps from allocating accessories to final makeup. These steps can be written in programming as methods and should be called while creating an instance of a specific car type. Provides an interface for creating objects in a superclass, but allows subclasses to alter the type of objects that will be created.

Types of Structural Design Patterns in Java:

Lets you ensure that a class has only one instance, while providing a global access point to this instance. All the code additions are similar to those done for the Petrol.java file. Null Object Method is a Behavioral Design Pattern, it is used to handle the absence of a valid object by providing an object that does nothing or provides default behavior. In our example, we’ll create a food ordering system that allows customers to order different types of dishes, such as pizza and sushi, using the Factory Pattern. The interpreter pattern is used to define a grammatical representation of a language and provides an interpreter to deal with this grammar.

Factory Design Pattern Super Class

We can see many realtime examples of factory pattern in JDK itself e.g. It also prevents us in making changes to car making process because the code is not centralized, and making changes in all composing classes seems not feasible. Behavioral design patterns are a subsetof design patterns in software development that deal with the communication and interaction between objects and classes. They focus on how objects and classes collaborate and communicate to accomplish tasks and responsibilities. Composite Method is structural design pattern, it’s used to compose objects into tree structures to represent part-whole hierarchies.

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The dependency injection pattern allows us to remove the hard-coded dependencies and make our application loosely-coupled, extendable, and maintainable. We can implement dependency injection in Java to move the dependency resolution from compile-time to runtime. Spring framework is built on the principle of dependency injection. The memento design pattern is used when we want to save the state of an object so that we can restore it later on. This pattern is used to implement this in such a way that the saved state data of the object is not accessible outside of the Object, this protects the integrity of saved state data.

The proxy pattern provides a placeholder for another Object to control access to it. This pattern is used when we want to provide controlled access to functionality. FactoryPatternDemo, our demo class will use ShapeFactory to get a Shape object. It will pass information (CIRCLE / RECTANGLE / SQUARE) to ShapeFactory to get the type of object it needs. Specifically, the Factory Method and Abstract Factory are very common in Java software development. And it must all be put into a single place so that you don’t pollute the program with duplicate code.

Behavioral patterns provide a solution for better interaction between objects and how to provide loose-coupling and flexibility to extend easily. The flyweight design pattern is used when we need to create a lot of Objects of a Class. The NotificationFactory class is responsible for constructing/creating objects for different types of notifications. The Factory Method separates product construction code from the code that actually uses the product. Therefore it’s easier to extend the product construction code independently from the rest of the code.

Lets you split a large class or a set of closely related classes into two separate hierarchies—abstraction and implementation—which can be developed independently of each other. Note that the parent class has been created, we can start creating the child classes. The visitor pattern is used when we have to perform an operation on a group of similar kinds of objects. With the help of a visitor pattern, we can move the operational logic from the objects to another class. Use the Factory to get object of concrete class by passing an information such as type. Create a Factory to generate object of concrete class based on given information.

We're going to create a Shape interface and concrete classes implementing the Shape interface. NotificationService as a driver class to demonstrate the factory method design pattern. There are different creational design patterns and they have their intent and applicability.

The factory design pattern says to define an interface ( A java interface or an abstract class) for creating the object and let the subclasses decide which class to instantiate. The factory design pattern is used when we have a superclass with multiple subclasses and based on input, we need to return one of the subclasses. This pattern takes out the responsibility of the instantiation of a Class from the client program to the factory class. We can apply a singleton pattern on the factory class or make the factory method static. The factory design pattern is used when we have a superclass with multiple sub-classes and based on input, we need to return one of the sub-class. This pattern takes out the responsibility of the instantiation of a class from the client program to the factory class.