Encapsulation - definition & overview

Encapsulation is a way to restrict the direct access to some components of an object, so users cannot access state values for all of the variables of a particular object. Encapsulation can be used to hide both data members and data functions or methods associated with an instantiated class or object.

Encapsulation in programming has a few key benefits. These include:

• Hiding data: Users will have no idea how classes are being implemented or stored. All that users will know is that values are being passed and initialized.
• More flexibility: Enables you to set variables as red or write-only. Examples include: setName(), setAge() or to set variables as write-only then you only need to omit the get methods like getName(), getAge() etc.
  
• Easy to reuse: With encapsulation, it's easy to change and adapt to new requirements

Java encapsulation

Object-oriented programming is one of the key pillars of Java. The concepts here refer to object-oriented programming as a whole and Java development. To become a Java developer, it is essential to understand the concepts of encapsulation, inheritance, abstraction and polymorphism.

Along with inheritance, encapsulation and abstraction form the three central principles of object-oriented programming.

What is inheritance in programming?

Inheritance is a mechanism that allows one class to gain the properties of another class in the same way that a child inherits some attributes from each of their parents. Inheritance allows programmers to create a new class that reuses an existing class's data members and methods.

What is abstraction in programming?

Abstraction occurs when a programmer hides any irrelevant data about an object or an instantiated class to reduce complexity and help users interact with a program more efficiently. The term abstraction vs encapsulation can describe the process of hiding some of the information contained in an object or class, but it may also refer to the object itself. An abstraction is any named entity that contains a selection of data and behaviors specific to a particular usage of the originating entity.

In the popular programming text Object-Oriented Analysis and Design, Grady Booch writes that:

"Abstraction and encapsulation are complementary concepts: abstraction focuses on the observable behavior of an object...encapsulation focuses on the implementation that gives rise to this behavior."

Stated differently, an abstraction relates to how an object and its behaviors are presented to the user and encapsulation is a methodology that helps create that experience.

Think about the interface of your mobile phone. Whether you use an Android operating system or iOS, you don't interact directly with the code that allows your phone to connect to the internet, send a text message or play a video game. Instead, you interact with the code through a user interface designed to streamline your experience and make accessing the functions and methods you need to complete a task easily. In this case, the interface is abstracted from the actual code implementation.

Containers are a relatively new type of software that can be used to virtually package a piece of code along with all of its libraries and other dependencies that it needs to execute. Containers create an encapsulated virtual environment where an application can be launched using the minimum storage space and computing power. A group of containers can share access to a single operating system and draw their computing resources from a single piece of hardware.

Encapsulation in OOP: containers vs. virtual machines

Containerization has emerged as an alternative to virtual machines because of its highly efficient usage of computing resources. Virtualization allowed multiple operating systems and applications to run simultaneously while sharing the resources of a single computer. Containers improved on this model by sharing a host operating system and installing the container runtime engine onto the host machine's operating system.

A computer running four virtual machines expends additional resources for each instance of the operating system that it runs, while a computer with an installed containerization engine could run the same number of applications on a single operating system. As a result, multiple containers can operate using the same computing capacity as a single virtual machine.

Containers are just one example of encapsulation in coding, where data and methods are bundled into a single package.

In the Java programming language, and in many other languages, information hiding is controlled using getter/setter methods for data attributes that will be readable or that may be updated by other classes.

Encapsulation in OOP: getter/setter methods

A getter method is used to retrieve the value of a specific variable within a class. A setter method is used to set or update the value of a specific variable within a class. Programmers can use access modifiers to define the visibility and accessibility of classes, along with the data and methods that they contain. In the Java programming language, there are four types of access modifiers to choose from:

• Private: When the private access modifier is applied to an attribute or method, it can only be accessed by code within the same class. As a result, the class will likely need to include getter and setter methods that can be used to access information about the attribute or to change its value. Variables that can only be accessed through getter and setter calls are encapsulated.
• Protected: A variable or method that is protected can be accessed by code within the same class, by any classes that are in the same package and by all sub-classes in the same or other packages.
• Public: The public access modifier is the least restrictive of all. Methods, attributes, and classes coded with this access modifier can be viewed and accessed by code within the same class and all other classes.
• No modifier: A variable with no access modifier can be accessed or viewed from within the same class or all other classes in the same package.

There are many benefits to hiding information about attributes and methods using encapsulation in programming. One is that it prevents other developers from writing scripts or APIs that use your code. With encapsulation, users of a class do not learn how a class stores its data, and the developer can change the data type of a field without forcing developers and users of the class to change their code.

IT organizations can implement encapsulation to protect sensitive data and maintain compliance with industry-specific data security and privacy requirements such as HIPAA and PCI DDS. The encapsulation process helps to compartmentalize data, limiting vulnerabilities by providing users with information on code implementations exclusively on a need-to-know basis.

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What is the Single Responsibility Principle?

The Single Responsibility Principle (SRP) is a fundamental principle in software development that states that a class should have only one reason to change, meaning it should have a single responsibility or job within the application. By adhering to the SRP, each class is focused on performing a specific task or function, making the codebase more modular and easier to understand, maintain, and test. This principle helps avoid code duplication, improves code reusability and enhances overall software design by promoting high cohesion and low coupling between classes.

What are the common pitfalls to avoid when implementing encapsulation in a software project?

To implement encapsulation effectively in a software project, developers should avoid common pitfalls such as over-encapsulation, over-reliance on getter and setter methods, ignoring access modifiers, incomplete encapsulation and violating the Single Responsibility Principle. Key practices include striking a balance between data protection and simplicity, using access modifiers appropriately, ensuring complete encapsulation of all relevant data and maintaining a single, well-defined purpose for each class.

What is a real-world example of encapsulation in popular programming languages other than Java?

In Python, encapsulation can be implemented using naming conventions and property decorators. By convention, attributes or methods prefixed with an underscore (_) indicate that they are intended to be private and should not be accessed directly from outside the class. For example, consider a class representing a bank account where the balance attribute should be private. In Python, you can achieve encapsulation by defining the balance attribute as "_balance" and providing getter and setter methods or using property decorators to encapsulate access to the balance attribute. This approach restricts direct access to the balance attribute, ensuring data integrity and control over how it is accessed and modified outside the class.