Encapsulation

Encapsulation

Encapsulation is the process of bundling data and the methods that operate on that data inside a class and restricting direct access to the internal data.

In simple words:

Encapsulation = Data hiding + Controlled access

Real-Life Example: Bank Account

Think about a bank account. You can deposit money, withdraw money, and check your balance, but you cannot directly change the balance to any value you want.

For example, you should not be able to directly set your balance to ₹1,00,00,000. Instead, the bank provides controlled operations such as deposit(), withdraw(), and getBalance(). The actual balance is kept private and can only be accessed or modified through these valid operations.

How Encapsulation Works in Java

There are a few important concepts involved:

Java Example

class BankAccount {
    private double balance;

    public void deposit(double amount) {
        if (amount > 0) {
            balance += amount;
        }
    }

    public void withdraw(double amount) {
        if (amount > 0 && amount <= balance) {
            balance -= amount;
        }
    }

    public double getBalance() {
        return balance;
    }
}

Using the Class

BankAccount account = new BankAccount();

account.deposit(1000);
account.withdraw(300);

System.out.println(account.getBalance()); // 700

Why is balance Private?

If balance were public:

class BankAccount {
    public double balance;
}

BankAccount account = new BankAccount();
account.balance = -5000; // Invalid value

Anyone could directly modify the balance.

By making it private:

class BankAccount {
    private double balance;
}

the outside code cannot directly access or modify it. Instead, it must go through methods where we can apply rules and validation.

Encapsulation vs Data Hiding

These terms are related but not exactly the same.

Key Benefits

Interview Definition

Encapsulation is an OOP principle that bundles data and the methods that operate on that data within a class while restricting direct access to the internal state.

Remember

Private data + controlled public methods = Encapsulation