How to convert a string into upper case?

Source:

public class StringToUpperCase {
   public static void main(String[] args) {
      String str = "abcdefghijflmnopqrstuvwxyz";
      String upper = str.toUpperCase();
      System.out.println(str);
      System.out.println(upper);
   }
}

Output:

   $ java StringToUpperCase 
   abcdefghijflmnopqrstuvwxyz
   ABCDEFGHIJFLMNOPQRSTUVWXYZ