A DESCRIPTION OF THE REQUEST :
A profile of an application heavily using String.format revealed that over 90% of the String.format runtime is spent on parsing the format strings. The application uses no more than 10-20 different format strings, each of which are used several million times.

JUSTIFICATION :
If java.util.Formatter could avoid repetitive parsing of format strings, a significant (90% in this case) of runtime could be saved.

EXPECTED VERSUS ACTUAL BEHAVIOR :
EXPECTED -
Either some sort of PreparedFormatter should be provided that reuses a previously parsed format string, or the Formatter class should cache format strings internally.
ACTUAL -
java.util.Formatter (re)parses format strings for each use.

---------- BEGIN SOURCE ----------
class T {
   public static void main (String[] args) {
      for (int i = 0;i < 1000000;i++) {
         System.out.format ("%d. %s%n",i,"Hello world!");
      }
   }
}

---------- END SOURCE ----------

CUSTOMER SUBMITTED WORKAROUND :
None identified.