day-19: Java Access Modifiers - Simplified

Encapsulation is one of the four fundamental OOP principles (along with Inheritance, Polymorphism, and Abstraction). It refers to bundling data (variables) and methods (functions) that operate on that data into a single unit (class), while restricting direct access to some of the object's components.

Types of Encapsulation:
Java Access Modifiers - Simplified
1). private
Access Level: Only within the same class
Example:

private int salary; // Only accessible in this class

Use Case: Hide sensitive data (e.g., passwords, internal calculations).

2). default (No Modifier)
Access Level: Only within the same package
Example:

String department; // Accessible only in this package

3). protected
Access Level:
Same package +
Subclasses (even in different packages)
Example:

protected String projectName; // Accessible in package + child classes

4). public
Access Level: Everywhere (global access)
Example:

public String companyName = "TechCorp"; // Accessible by any class

Use Case: APIs, constants, or methods needed globally.

Note:
public static void main(String[] args) - //Method Signature
Access Specifier not for local variables

When to Use Which?
private: Hide internal implementation details.
default: Share code within a package only.
protected: Allow controlled inheritance.
public: Expose APIs/constants.

Example:

public class Employee {
    private int id;          // Only this class
    String name;             // Package-only (default)
    protected String role;   // Package + child classes
    public static final String COMPANY = "TechCorp"; // Global
}

Class Example:

public class Google {

    private int emp_salary; 
    public static String ho_address = "Mountain View"; 
    public static boolean working = true; 

    private void get_user_details() {
        int no = 10; 
        System.out.println("All Users Details");
    }

    public void search_Results() {
        System.out.println("Searching Results"); 
    }

}


public class User {
    public static void main(String[] args) { //Method Signature
        Google googleObj = new Google() ;
        //System.out.println(googleObj.emp_salary); 
        System.out.println(Google.working);
        System.out.println(Google.ho_address);

        //googleObj.get_user_details(); 
        googleObj.search_Results(); 
        User.main(); 
    }

    public static void main(){     
        System.out.println("Overloaded Main Method");
    }
}

Key Rules
Class-level: Only public or default (no private/protected).
Variables/Methods: All 4 modifiers allowed.
Security Tip: Start with private, widen access only when needed.
This ensures encapsulation while providing flexibility. 🚀

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