What is Encapsulation?

Encapsulation in Java OOPs with Example


What is Encapsulation in Java?

Encapsulation is a principle of wrapping data (variables) and code together as a single unit. It is one of the four OOP concepts. The other three are Inheritance, Polymorphism, and Abstraction.

In this tutorial, you will learn-

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Learn Encapsulation with an Example

To understand what is encapsulation in detail consider the following bank account class with deposit and show balance methods

Suppose a hacker managed to gain access to the code of your bank account. Now, he tries to deposit amount -100 into your account by two ways. Let see his first method or approach.

Approach 1: He tries to deposit an invalid amount (say -100) into your bank account by manipulating the code.

Learn Java Encapsulation in 10 Minutes

Now, the question is – Is that possible? Let investigate.

Usually, a variable in a class are set as “private” as shown below. It can only be accessed with the methods defined in the class. No other class or object can access them.

Learn Java Encapsulation in 10 Minutes

If a data member is private, it means it can only be accessed within the same class. No outside class can access private data member or variable of other class.

So in our case hacker cannot deposit amount -100 to your account.

Learn Java Encapsulation in 10 Minutes

Approach 2: Hacker’s first approach failed to deposit the amount. Next, he tries to do deposit a amount -100 by using “deposit” method.

Learn Java Encapsulation in 10 Minutes

But method implementation has a check for negative values. So the second approach also fails.

Learn Java Encapsulation in 10 Minutes

Thus, you never expose your data to an external party. Which makes your application secure.

Learn Java Encapsulation in 10 Minutes

The entire code can be thought of a capsule, and you can only communicate through the messages. Hence the name encapsulation.

Data Hiding in Java

Frequently, Java encapsulation is referred as data hiding. But more than data hiding, encapsulation concept is meant for better management or grouping of related data.

To achieve a lesser degree of encapsulation in Java, you can use modifiers like “protected” or “public”. With encapsulation, developers can change one part of the code easily without affecting other.

Getter and Setter Methods in Java

If a data member is declared “private”, then it can only be accessed within the same class. No outside class can access data member of that class. If you need to access these variables, you have to use public “getter” and “setter” methods.

Getter and Setter’s methods are used to create, modify, delete and view the variables values.

The following code is an example of getter and setter methods:

In above example, getBalance() method is getter method that reads value of variable account_balance and setNumber() method is setter method that sets or update value for variable account_number.