Public And Private

Private properties and functions can be accessed or modified only in the class body.

Public members can be accessed or modified anywhere - class body, main function, other function.

It can be understood via the following code:

class Person { private // set default value for id String id = "1"; public String name; int age; void printData() { System.out.println("Name: " + name); System.out.println("Age: " + age); System.out.println("Id: " + id); } }; public class Main { public static void main(String[] args) { Person personObject = new Person(); personObject.name = "John"; personObject.age = 20; // personObject.id = "new_id"; personObject.printData(); } }

Output:

Name: John Age: 20 Id: 1

There are a couple of things to notice about the private property id and the public properties name and age:

• Both public and private properties can be accessed/modified in the class body: for public properties - lines 13 and 14, for private properties - line 15.
• Outside the Person class body (like the main function) only public properties can be accessed/modified - lines 24 and 25.
• If we uncomment line 26 the code will not compile. Because a private member (id in this case) cannot be accessed/modified outside the Person class body.