Encapsulation Basics

Data hiding and bundling

Interview Relevant: Core OOP principle
4 min read

Encapsulation in Java

Encapsulation is the practice of wrapping data (variables) and methods together and restricting direct access to the data.

Key Idea: Protect internal state using private access and expose behavior via methods.

Code Examples

Data hiding using private variables

java
1
2class BankAccount {
3    private double balance; // hidden data
4
5    public void deposit(double amount) {
6        if (amount > 0) {
7            balance += amount;
8        }
9    }
10
11    public double getBalance() {
12        return balance;
13    }
14}
15
16BankAccount acc = new BankAccount();
17acc.deposit(1000);
18// acc.balance = 5000; // āŒ Not allowed
19System.out.println(acc.getBalance());
20

Use Cases

  • Protecting object state
  • Preventing invalid data modification
  • API stability

Common Mistakes to Avoid

  • Using public fields
  • Exposing internal state directly