src/share/classes/java/text/NumberFormat.java

*** 281,294 ****
--- 281,304 ----
       * @exception        ArithmeticException if rounding is needed with rounding
       *                   mode being set to RoundingMode.UNNECESSARY
       * @see java.text.Format#format
       */
      public final String format(double number) {
+         // Use fast-path for double result if that works
+         String result = fastFormat(number);
+         if (result != null) return result;
+ 
          return format(number, new StringBuffer(),
                        DontCareFieldPosition.INSTANCE).toString();
      }
  
+     /*
+      * fastFormat() is supposed to be implemented in concrete subclasses only.
+      * Default implem always returns null.
+      */
+     String fastFormat(double number) { return null; }
+ 
     /**
       * Specialization of format.
       * @exception        ArithmeticException if rounding is needed with rounding
       *                   mode being set to RoundingMode.UNNECESSARY
       * @see java.text.Format#format