dun understand on DateFormat

[ming ming]

below is the exam watch from k&b book which i dun understand it. Someone mind to explain it to me:
"Both DateFormat and NumberFormat objects can have their locales set only at the time of instantiation. Watch for code that attempts to change the lcoale of an existing instance-no such method exist!"
Preferbaly someone show example. thanks

[Deepak Bala]

This is what they meant.

 
import java.util.*;
import java.text.*;
class test 
{
   public static void main( String args[] )
   {
      DateFormat df = DateFormat.getDateInstance(0 , Locale.ENGLISH);
      df.changeLocale( Locale.FRANCE ); // 2
   }
}
 

   

Note that line 2 will not compile and no such method exists that can change the locale after instantiating the object pointed to by df