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Therefore, you need to have a regular method capable of creating new objects as well as reusing existing ones. Imagine that you write an app using an open source UI framework. Your app should have round buttons, but the framework only provides square ones.
What is the Factory Design Pattern?
Pankaj, You have a wide reach and your article make a huge impact on developers. I appreciate your work and dedication that you put to bring this in front of us all. Having said that I want to invite you to partner me in clearing the space and providing the correct Design patterns as they are and not as they occur to you, me or any other author. I want to point out that the example you have put is neither of that.
Important Topics for the Factory Method in Java Design Patterns
For a start, classes in java or any other object-oriented programming language are generally written in a way that leads to coupling problems, unless design patterns are used. Subclasses get highly dependent on each other when the code gets larger and larger and that is where the real problem begins. This cannot go on forever and we need some elegant way to avoid such a situation. Factory Method is a creational design pattern that provides an interface for creating objects in a superclass, but allows subclasses to alter the type of objects that will be created. The Factory Design Pattern is a creational design pattern that provides a simple and flexible way to create objects, decoupling the process of object creation from the client code.
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Creational Software Design Patterns in Java
In this post, I will demonstrate another creational pattern, i.e. Factory, as the name suggests, is a place to create some different products which are somehow similar in features yet divided into categories. With the Factory Pattern, the object creation logic is hidden from the client. Instead of knowing the exact object class and instantiating it through a constructor, the responsibility of creating an object is moved away from the client. Super class in factory design pattern can be an interface, abstract class or a normal java class. For our factory design pattern example, we have abstract super class with overridden toString() method for testing purpose.
Square Implementation
In my previous post, “Singleton design pattern in java“, we discussed various ways to create an instance of a class such that there can not exist another instance of same class in same JVM. It's a misconception that design patterns are holy solutions to all problems. Design patterns are techniques to help mitigate some common problems, invented by people who have solved these problems numerous times. This is an interface or an abstract class that declares the method for creating objects. In the example, CurrencyFactory is the factory interface with the method createCurrency().
Pentagon Implementation
As long as all product classes implement a common interface, you can pass their objects to the client code without breaking it. This approach separates the object creation from the implementation, which promotes loose coupling and thus easier maintenance and upgrades. For this reason, design patterns have become the de facto standard in the programming industry since their initial use a few decades ago due to their ability to solve many of these problems.
In this article I'll demonstrate a small-but-complete example of the Factory Pattern (also known as the “Factory Design Pattern” and “Factory Method”) implemented in Java. StackTips provides programming tutorials, how-to guides and code snippets on different programming languages. The above example is working great to deal with producing mobiles. However, we have outlined some of the problems above on the above approach. And it must all be put into a single place so that you don’t pollute the program with duplicate code.
AccountType consists of fixed values that have been predefined in the banking industry domain; therefore, it is a constant, and we use Enum for this data type to ensure integrity. First, we create a BankAccount, which is an abstract class that will contain information commonly used for specific Accounts. First of all, notice that we have taken the createDrink method from the DrinkFactory class and have put that into the DrinkCafe class and also declared createDrink as an abstract method. Also, it’s important to note that in this simple example I’m only accepting strings like "small", "big", and "working" as my "criteria". In a more complicated (real world) example, you’ll want to tighten down this code much more.
Advantages of Factory Method Design Pattern in Java
In other words, subclasses are responsible to create the instance of the class. Factory method is a creational design pattern which solves the problem of creating product objects without specifying their concrete classes. We are taking here an example of different shapes like Circle, Rectangle and Square. We will create an interface (Shape) and sub classes will implement this Shape interface. We will create ShapeFactory to get the different shape type objects.
Adding a new class to the program isn’t that simple if the rest of the code is already coupled to existing classes. CarType will hold the types of car and will provide car types to all other classes. Sooner or later, a desktop program, mobile app, or some other type of software will inevitably become complex and start exhibiting certain kinds of problems. These problems are typically related to the complexity of our codebase, non-modularity, inability to separate certain parts from each other, etc. As you can see from my driver class, I create an instance of each type of dog (small, big, and working).
Secondly, this pattern minimizes the dependency between classes. For example, in the future, there might be new types of accounts such as Credit, Debit, etc. At that time, we only need to create additional subclasses that extend BankAccount and add them to the factory method.
Now let's explore the ways to implement the Factory design pattern together. From the class diagram, coders can easily see that the implementation for Factory is extremely straightforward. AccountFactory takes an AccountType as input and returns a specific BankAccount as output. We have used simple factory design pattern examples in java for demonstrational purposes. You define a base class type (or in this case an interface), and then have any number of subclasses which implement the contract defined by the base class.
For now, they have two successful products SpiceFire and SpiceBolt. The produceMobile() method is working well which produce two different mobiles based on their model number. Let us have a look into the current implementation of produceMobile() method.
Any changes that may occur inside any subclass will eventually force us to make changes to the drinkCafe class as well. It should be pretty clear that reducing dependencies to concrete classes in our code should be considered a “good thing”. Base dialog works with products using their common interface, that’s why its code remains functional after all changes. Factory pattern is most suitable where there is some complex object creation steps are involved. To ensure that these steps are centralized and not exposed to composing classes, factory pattern should be used.
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