use of final key word...

public class fin1 //super class
{
final int a=10;
}
public class fin extends fin1 // base class
{

public static void main(String arg[])
{
int a=12; int b=20;
fin f =new fin();
int c=a+b;
System.out.println(c); //ans is 32
c=f.a+b;
System.out.println(c); //ans is 30
}
}