What is encapsulation in object-oriented programming (OOP)?

Encapsulation is a mechanism that combines data and methods (functions) that work with this data into a single object. The implementation details of the object are hidden from the outside world, providing access to the data only through a specific interface (public methods).

Main goals:

• Data hiding: Prevents direct access to the internal states of the object, protecting them from incorrect modification.
• Access control: Allows defining which parts of the object are accessible from outside.
• Manageability: Simplifies changing the internal implementation without affecting the code that uses this object.
• Security: Ensures data integrity.

Example in Java:

class BankAccount {
    private double balance; // Data is hidden

    public BankAccount(double initialBalance) {
        if (initialBalance >= 0) {
            this.balance = initialBalance;
        } else {
            this.balance = 0;
        }
    }

    public double getBalance() { // Public method for access
        return balance;
    }

    public void deposit(double amount) { // Public method for modification
        if (amount > 0) {
            balance += amount;
        }
    }

    public void withdraw(double amount) { // Public method for modification
        if (amount > 0 && balance >= amount) {
            balance -= amount;
        }
    }
}

// Usage example
// BankAccount account = new BankAccount(1000);
// double currentBalance = account.getBalance(); // Access via method
// account.deposit(500); // Modification via method
// account.balance = -100; // Cannot directly change balance