I am producing a file that needs English/ASCII/C Locale. One part calls

   public static String yearday(Date d) {
    return String.format(null, "%te.%tb.%tY", d, d, d);
   }

String.format documentation says the Local can be null:

    l - The locale to apply during formatting. If l is null then no localization
    is applied. This does not change this object's locale that was set during
    construction.

However, attempting to pass the null Locale yields:

Exception in thread "main" java.lang.NullPointerException
        at java.util.Calendar.createCalendar(Calendar.java:962)
        at java.util.Calendar.getInstance(Calendar.java:937)
        at java.util.Formatter$FormatSpecifier.printDateTime(Formatter.java:2738)
        at java.util.Formatter$FormatSpecifier.print(Formatter.java:2651)
        at java.util.Formatter.format(Formatter.java:2430)
        at java.util.Formatter.format(Formatter.java:2364)
        at java.lang.String.format(String.java:2564)
        at com.sun.WHATEVER.yearday(MYFILE.java:191)
###@###.### 2005-06-08 01:18:51 GMT