What are Access Modifiers in Java? Java में Access Modifiers क्या हैं?

Access modifiers control the visibility and accessibility of classes, methods, and variables. Java has four access levels: public, protected, default (package-private), and private.

// Access Modifiers Example
public class AccessModifierDemo {
    // Public - accessible everywhere
    public int publicVar = 10;
    public void publicMethod() {
        System.out.println('Public method');
    }
    
    // Protected - accessible in same package and subclasses
    protected int protectedVar = 20;
    protected void protectedMethod() {
        System.out.println('Protected method');
    }
    
    // Default (package-private) - accessible in same package only
    int defaultVar = 30;
    void defaultMethod() {
        System.out.println('Default method');
    }
    
    // Private - accessible only in same class
    private int privateVar = 40;
    private void privateMethod() {
        System.out.println('Private method');
    }
}

// Same package, different class
public class SamePackage {
    public static void main(String[] args) {
        AccessModifierDemo obj = new AccessModifierDemo();
        
        obj.publicVar;          // ✓ Accessible
        obj.publicMethod();     // ✓ Accessible
        obj.protectedVar;       // ✓ Accessible
        obj.protectedMethod();  // ✓ Accessible
        obj.defaultVar;         // ✓ Accessible
        obj.defaultMethod();    // ✓ Accessible
        // obj.privateVar;       // ✗ Compile Error
        // obj.privateMethod();  // ✗ Compile Error
    }
}

// Different package
public class DifferentPackage {
    public static void main(String[] args) {
        AccessModifierDemo obj = new AccessModifierDemo();
        
        obj.publicVar;          // ✓ Accessible
        obj.publicMethod();     // ✓ Accessible
        // obj.protectedVar;     // ✗ Compile Error (unless subclass)
        // obj.defaultVar;       // ✗ Compile Error
        // obj.privateVar;       // ✗ Compile Error
    }
}

// Best Practices:
// 1. Use private for data members (encapsulation)
// 2. Use public for public API methods
// 3. Use protected for methods meant for subclasses
// 4. Use default only when intentional (package-level access)