Private vs Protected vs Final Access Modifier in Java

Whenever we are writing our classes, we have to provide some information about our classes to the JVM like whether this class can be accessed from anywhere or not, whether child class creation is possible or not, whether object creation is possible or not, etc. we can specify this information by using an appropriate keyword in java called access modifiers. So access modifiers are used to set accessibility of classes, methods, and other members.

Access modifiers:

1. Private
2. Protected
3. Final

Let us do discuss them in-depth to get a better understanding before getting to the differences between them.

Private Access Modifier: This modifier is not applicable for top-level classes or interfaces. It is only applicable to constructors, methods, and fields inside the classes. If a variable or methods or constructor is declared as private as we can access them only from within the class i.e from outside the class we can’t access them.

Java

// Java Program to illustrate Private Access Modifier

// Importing required packages
import java.io.*;
import java.util.*;

// Class 1
// Helper class
class A {

    // Method of this class
    private void m1() {

        // Print statement whenever this method is called
        System.out.println("GFG");
    }
}

// Class 2
// Main class
class B {

    // Main driver method
    public static void main(String[] args) {
        // Creating an object of above class
        A a = new A();

        // Accessing the method m1() of above class
        // by creating object of above class in
        // main() method of this class
        a.m1();
    }
}

Protected Access Modifier: This modifier can be applied to the data member, method, and constructor, but this modifier can’t be applied to the top-level classes and interface. A member is declared as protected as we can access that member only within the current package but only in the child class of the outside package.

Java

// Java program to illustrate Protected Access Modifier
// import required packages
import java.io.*;
import java.util.*;

// declaring a parent class A
class A {

    // declaring a protected method m1()
    protected void m1() { System.out.println("GFG"); }
}

// creating a child class by extending the class A
class B extends A {

    // main method
    public static void main(String[] args)
    {
        // creating an object of parent class
        // using parent reference
        A a = new A();

        /// calling method m1
        a.m1();

        // creating an object of child class
        // using child reference
        B b = new B();

        // calling method m1
        b.m1();

        // creating an object of child class
        // using parent reference
        A a1 = new B();

        // calling m1 method
        a1.m1();
    }
}

Output

GFG
GFG
GFG

Output Explanation: In the above example, we create three objects using parent reference and child reference and call m1() method on it, and it successfully executed so from the above example we can say that we can access the protected method within the current package anywhere either by using parent reference or by child reference.

Final Access Modifier: It is a modifier applicable to classes, methods, and variables. If we declare a parent class method as final then we can’t override that method in the child class because its implementation is final and if a class is declared as final we can’t extend the functionality of that class i.e we can’t create a child class for that class i.e inheritance is not possible for final classes. Every method present inside the final class is always final y default, but every variable present inside the final class need not be final. The main advantage of the final keyword is we can achieve security and we can provide a unique implementation. But the main disadvantage of the final keyword is we are missing key benefits of OOPs like Inheritance(Because of the final class), Polymorphism(Because of the final method)  hence if there are no specific requirements then it is not recommended to use the final keyword. 

Java

// Java program to illustrate Final keyword

// import required packages
import java.io.*;
import java.util.*;
// Declaring parent class P
class P {
    // Declaring a first name
    // method
    public void firstName()
    {
        // Display firstname
        System.out.println("Rahul ");
    }
    /// Declaring a final surName
    // method
    public final void surName()
    {
        // Display surname
        System.out.println("Trivedi");
    }
}
// Creating a child class
// of above parent class
class C extends P {
    // overriding the surName
    // method
    public void surName()
    {
        // Display surname
        System.out.println("Sharma");
    }
    // Main method
    public static void main(String[] args)
    {
        // Display message
        System.out.println("GFG");
    }
}

Output:

Now after having an understanding of all of them let us do land on differences between them to conclude out.

Private Access Modifier	Protected Access Modifier	Final Access Modifier
This modifier is not applicable to top-level classes.	This modifier is not applicable to top-level classes.	This modifier is applicable to top-level classes.
This modifier is applicable to both the enum and constructor.	This modifier is applicable to both the enum and constructor.	The final modifier is not applicable to both the enum and constructor.
This modifier is applicable to interfaces.	This modifier is applicable to interfaces.	This modifier is not  applicable to interfaces
This modifier is not applicable to local variables.	This modifier is not applicable to local variables.	This modifier is the only modifier that is applicable to local variables.
We cannot access private members outside the class.	We can access the protected members outside the class.	We can access the final members outside the class.
We cannot access private members from the outside package.	We can access protected members from the outside package through child reference.	We cannot access final members from the outside package.