Java, which was owned by Oracle, is a multi-platform, object-oriented programming language with first-class functioning. It is widely used by developers for many years since it supports portability and is extensively dynamic.
The review is majorly focused on the major aspects of design patterns in software engineering, the structure, and the categorization of the Java design patterns. Moving on, the review will also comprise the major subcategories of the design patterns and will mainly focus on 5 main design patterns that are widely used.
What are design Patterns in software engineering
The sole basis of software engineering is centered around design patterns. A software design pattern is a software template, simply introduced as a general solution to routine problems in software designing. All patterns are unique with a blueprint that could be customized accordingly to solve a design problem in any code in the software development lifecycle.
Why do we need software design patterns?
Design patterns are needed majorly to support object-oriented programming language which is paradigm based on the concepts of both objects and classes. These design patterns are unique and are proven to provide a reliable solution to common problems and therefore there is no reinvention of the problem. The software design patterns are reusable and can be modified accordingly. The presence of design factors prevents refactoring since the optimal solution for the problem is found.
Structure of a design pattern
The structure of all software design patterns are well organized and is often documented as a template. The main system of software design patterns consists of a patent name, intent, applicability, structure, participants, collaborations, and consequences. This structure has been introduced by the Authors of the book called the Java Design Patterns. Commonly called the Gang of Four, Erich Gamma, Richard Helm, Ralph Johnson, and John Vissides are the pioneers in software design patterns.
Categorization of Java Design Patterns
Accordingly, design in patterns in Java is initially divided into 4 major categories as mentioned below,
- Creational Design Patterns
This design pattern is involved with the method of creating objects.
- Structural Design Patterns
This includes the collaboration of objects and classes that aids in forming larger structures
- Behavioral design patterns
The above design patterns focus on the interaction between objects
- JEE design patterns
Majorly involved in providing solutions to Java EE-based software frameworks.
Software designing comprises around 23 software designing patterns that fall into either of the above categories and they are called the gang of four design patterns. Out of the 23, 5 most essential design patterns have been navigated essentially by many in the gang of four design patterns
The Most Essential Design Patterns
The design patterns introduced are as follows,
- Factory Pattern
- Singleton Pattern
- Facade Pattern
- Adaptor Pattern
- Strategy Pattern
Thereby, an overview of the 5 most essential gangs of four design patterns in Java is as follows,
- Factory Design Pattern.
This Factory Pattern, also called the virtual constructor, belongs to the creational design pattern. As the category defines it involves the creation of an object. The factory design pattern follows the point of ‘Define an interface or abstract class for creating an object but let the subclass decide which class to instantiate. For the instantiation, there are one or more concrete subclasses in the design pattern. Just as the name implies, ‘Factory’ is involved in the creation of products. Furthermore, the logic of the creation of the object is hidden from the client.
The points of implementation of the Factory design patterns include,
Defining the factory method within the interface
Allowing the subclass to decide on the implementation and the object to be created.
Although Java constructors are not polymorphic, in this factory design pattern we achieve pseudo polymorphism. This is because the subclass was allowed to decide on the creation.
- Singleton Design Pattern
Belonging to the gang of four design patterns, the singleton design pattern falls under the creational design pattern category. Thereby, it follows the principle ‘define a class that has only one instance and provides a global point of access to it’. This design pattern is considered to be one of the simplest Java design patterns. The design restricts a class to instantiate multiple objects. And only a single instance of the class is required for the entire execution. Early initialization and lazy initialization are the two methods of instantiation of the design pattern. Early initialization is simple and the class is initialized whether or not it is being used. While, in lazy initialization, the initiation of the class happens only as required.
In this pattern of design, 4 methods of implementation could be seen.
Method 1 – Classic implementation
Method 2 – Synchronization of getInstance()
Method 3 – Eager Instantiation
Method 4 – Double-checked locking
- Facade design Pattern.
Categorized under the structural design patterns. The design patterns mask the complexity of the system and provide an interface for the client to access the system from the place he is. It is a higher level of interface and is easy to use. This design pattern is used in many franchise organizations.
- Adaptor Design Pattern
This design pattern, also called the wrapper, involves providing the interface to the client according to their requirements. Also, the services of the class could be gained with a different interface. This a pattern that is easily understood and the usage of this pattern is as follows,
-Request of the client to the adaptor by a method using the target interface
– Translation of the request of the adapter on the interface by the adaptor
-Receiving the results from the client.
The adaptor design pattern is highly reusable and flexible and uncomplicated. Nevertheless, it is widely used and essentially known by software engineers. Yet, since many adaptations are needed and all requests are forwarded, there might be a slight delay.
- Strategy Design Pattern
This falls under the behavioral design patterns and is also known as Policy and simply defines an algorithm family. This involves designing a family of functionality, collaborating with each one, and making them unchangeable. This is also a widely used object-oriented programming language. Basically, algorithms are encapsulated in a separate class that implements a common interface. This pattern consists of three main components,
- Context – the class with the object where the behavior is required to be changed dynamically
- Concrete – implementation of the strategy with the actual implementation
- Strategy – Implemented by the concrete component.
This design pattern has high flexibility, modularity, and testability, However, this may have increased complexity due to the usage of multiple classes.
JEE Design Patterns and Other Subcategories
The Jee design patterns include majorly MVC design patterns, DAO design patterns, business delegate patterns, intercepting patterns, service locator patterns, and transfer object patterns Along with these, other design patterns that fall into the major categories such as prototype patterns, builder pattern, and object pool pattern, composite pattern, mediator pattern, etc are also used in software engineering. Yet, these are not reliable as the 5 most essential patterns implicated above.
Benefits of Java Design Patterns
The benefits are immense and uncountable. These design patterns are reusable and define the system architecture. They are involved in capturing the software and provide transparency for the design of an application. The design patterns are proven and tested with solutions upon the best knowledge and expertise.
With the development of the technological world, Java design patterns are extremely essential for software engineering. Nonetheless, the gang of four design patterns plays an important role in the field. Out of these, the factory pattern, singleton pattern, strategy pattern, facade pattern, and adaptor patterns are handpicked as the most essential to be known by any software engineer.