🛡️ Encapsulation

Encapsulation is one of the four fundamental Object-Oriented Programming (OOP) concepts in Java, alongside Abstraction, Inheritance, and Polymorphism. It is the technique of wrapping data (variables) and code (methods) together as a single unit while restricting direct access to the data from outside the class.

A simple analogy for encapsulation is a capsule in medicine, where the active ingredients (data) are enclosed inside a protective shell (methods). This ensures that the contents are not directly accessible but can be utilized safely when needed.

Advantages of Encapsulation

Data Hiding - It prevents unauthorized access and modification of data.
Improved Maintainability - Encapsulation makes code more modular and easier to maintain.
Enhanced Flexibility - Controlled access allows modifications without breaking dependent code.
Increased Reusability - Encapsulated classes can be reused in different parts of an application.

Access Modifiers and Access Levels

Java provides four access modifiers to control the visibility of class members:

Access Modifier	Class	Package	Subclass	World
private	✅	❌	❌	❌
default (no modifier)	✅	✅	❌	❌
protected	✅	✅	✅	❌
public	✅	✅	✅	✅

Order of Restriction (from highest to lowest):

private (Most restrictive)
Default (No modifier)
protected
public (Least restrictive)

Example Programs

Encapsulation with Private Variables and Getters/Setters

class Person {
    private String name;
    private int age;
    
    // Constructor
    public Person(String name, int age) {
        this.name = name;
        this.age = age;
    }
    
    // Getter methods
    public String getName() {
        return name;
    }
    
    public int getAge() {
        return age;
    }
    
    // Setter methods
    public void setName(String name) {
        this.name = name;
    }
    
    public void setAge(int age) {
        if(age > 0) {
            this.age = age;
        }
    }
    
    // toString method
    @Override
    public String toString() {
        return "Person{name='" + name + "', age=" + age + "}";
    }
}

public class Main {
    public static void main(String[] args) {
        Person p = new Person("John", 25);
        System.out.println(p);
        
        p.setAge(30);
        System.out.println("Updated Age: " + p.getAge());
    }
}

Explanation

The name and age fields are private, ensuring data hiding.
Getter and setter methods provide controlled access to the fields.
The toString() method returns a string representation of the object.
Just like a capsule, encapsulation ensures that data is protected and only accessible through safe methods.

Encapsulation enhances security, maintainability, and reusability, making it an essential concept in Java development.

🔗 Related Topics: