Java Encapsulation

🔒 What is Encapsulation?

Encapsulation is hiding internal data and providing controlled access through methods. It protects class data from unauthorized access and maintains data integrity in object-oriented programming.


// Simple encapsulation example
public class Student {
    private String name;  // Hidden data
    
    public void setName(String name) {  // Controlled access
        this.name = name;
    }
    
    public String getName() {
        return name;
    }
}

Output:

Data is protected and accessed through methods

Key Encapsulation Concepts

🔐

Private Fields

Hide data from outside access

private int age;

📝

Getter Methods

Provide read access to private data

public int getAge() {
    return age;
}

✏️

Setter Methods

Provide controlled write access

public void setAge(int age) {
    if(age > 0) this.age = age;
}

🛡️

Data Validation

Ensure data integrity

if(email.contains("@")) {
    this.email = email;
}

🔹 Complete Encapsulation Example

Here's a fully encapsulated class with validation:

public class BankAccount {
    private String accountNumber;
    private double balance;
    private String ownerName;
    
    // Constructor
    public BankAccount(String accountNumber, String ownerName) {
        this.accountNumber = accountNumber;
        this.ownerName = ownerName;
        this.balance = 0.0;
    }
    
    // Getter methods
    public String getAccountNumber() {
        return accountNumber;
    }
    
    public double getBalance() {
        return balance;
    }
    
    public String getOwnerName() {
        return ownerName;
    }
    
    // Controlled methods for balance
    public void deposit(double amount) {
        if(amount > 0) {
            balance += amount;
            System.out.println("Deposited: $" + amount);
        }
    }
    
    public void withdraw(double amount) {
        if(amount > 0 && amount <= balance) {
            balance -= amount;
            System.out.println("Withdrawn: $" + amount);
        } else {
            System.out.println("Invalid withdrawal amount");
        }
    }
}

Usage:

BankAccount account = new BankAccount("12345", "John");
account.deposit(1000.0);
account.withdraw(500.0);
System.out.println("Balance: $" + account.getBalance());

🔹 Benefits of Encapsulation

Data Security: Private fields prevent unauthorized access
Data Validation: Setters can validate input before storing
Flexibility: Internal implementation can change without affecting users
Maintainability: Easier to debug and modify code

public class Person {
    private int age;
    
    public void setAge(int age) {
        // Validation ensures data integrity
        if(age >= 0 && age <= 150) {
            this.age = age;
        } else {
            System.out.println("Invalid age!");
        }
    }
    
    public int getAge() {
        return age;
    }
}