Difference between public static and private static variables

Question

class Employee{
 // salary  variable is a private static variable
private static double salary;

// DEPARTMENT is a constant
 public static final String DEPARTMENT = "Development";

public static void main(String args[]){
   salary = 1000;
  System.out.println(DEPARTMENT+  "  average salary:"+salary);
}
}

This java program contains a static variable. But I cannot understand the difference between public and private static variables.

Answer 1

A public variable is accessible everywhere in the code - a private variable is only accessible within the class itself. In this case you're using Employee.salary within the Employee class, so that's fine.

Note that the variable being static is a completely separate matter - and methods and classes have accessibility in the same way as variables.

There are other levels of access available too - protected and the default "package" access (which can't be specified explicitly). See section 6.6 of the Java Language Specification for more details.

(As a side matter, it's also worth learning about what static means - you almost certainly don't want these variables to be statics, as they apply to each Employee rather than the Employee concept in general. It's odd for DEPARTMENT to be a constant here, too.)

Answer 2

• A public variable is accessible from anywhere (well, anywhere where the class is accessible).

• A private variable is only accessible inside the class.

• A static variable belongs to the class rather than to an instance of a class.

• Notice that the variable DEPARTMENT is also final, which means that it cannot be modified once it is set. This is important here because that's what saves this from being bad code -- the variable is a constant so it's okay to give things outside the class access to it.