What is the modifier used on a class so that its members can be accessed by another class and can not be accessed by subclasses or other classes in a different package?

Modifiers

By now, you are quite familiar with the public keyword that appears in almost all of our examples:

The public keyword is an access modifier, meaning that it is used to set the access level for classes, attributes, methods and constructors.

We divide modifiers into two groups:

• Access Modifiers - controls the access level
• Non-Access Modifiers - do not control access level, but provides other functionality

Access Modifiers

For classes, you can use either public or default:

For attributes, methods and constructors, you can use the one of the following:

Non-Access Modifiers

For classes, you can use either final or abstract:

For attributes and methods, you can use the one of the following:

Final

If you don't want the ability to override existing attribute values, declare attributes as final:

Example

public class Main {
  final int x = 10;
  final double PI = 3.14;

  public static void main(String[] args) {
    Main myObj = new Main();
    myObj.x = 50; // will generate an error: cannot assign a value to a final variable
    myObj.PI = 25; // will generate an error: cannot assign a value to a final variable
    System.out.println(myObj.x);
  }
}

Try it Yourself »

Static

A static method means that it can be accessed without creating an object of the class, unlike public:

Example

An example to demonstrate the differences between static and public methods:

public class Main {
  // Static method
  static void myStaticMethod() {
    System.out.println("Static methods can be called without creating objects");
  }

  // Public method
  public void myPublicMethod() {
    System.out.println("Public methods must be called by creating objects");
  }

  // Main method
  public static void main(String[ ] args) {
    myStaticMethod(); // Call the static method
    // myPublicMethod(); This would output an error

    Main myObj = new Main(); // Create an object of Main
    myObj.myPublicMethod(); // Call the public method
  }
}

Try it Yourself »

Abstract

An abstract method belongs to an abstract class, and it does not have a body. The body is provided by the subclass:

Example

// Code from filename: Main.java
// abstract class
abstract class Main {
  public String fname = "John";
  public int age = 24;
  public abstract void study(); // abstract method
}

// Subclass (inherit from Main)
class Student extends Main {
  public int graduationYear = 2018;
  public void study() { // the body of the abstract method is provided here
    System.out.println("Studying all day long");
  }
}
// End code from filename: Main.java

// Code from filename: Second.java
class Second {
  public static void main(String[] args) {
    // create an object of the Student class (which inherits attributes and methods from Main)
    Student myObj = new Student();

    System.out.println("Name: " + myObj.fname);
    System.out.println("Age: " + myObj.age);
    System.out.println("Graduation Year: " + myObj.graduationYear);
    myObj.study(); // call abstract method
  }
}

Try it Yourself »

What is the modifier used on a class so that it's members can be accessed by another class and can not be accessed by subclasses or other classes in a different package?

What modifier is used when the class is accessible by any other class?

Which access modifier is used to access members only to the members of that class?

Which of the following access modifier can be accessed with in a class?