A DESCRIPTION OF THE REQUEST :
The Last three JavaDoc examples throws an Exception (Cannot be parsed):
https://docs.oracle.com/javase/8/docs/api/java/time/Duration.html#parse-java.lang.CharSequence-

Without Date Values it must start with "PT" :
    "PT-6H3M" -- parses as "-6 hours and +3 minutes"
    "-PT6H3M" -- parses as "-6 hours and -3 minutes"
    "-PT-6H+3M" -- parses as "+6 hours and -3 minutes"

JUSTIFICATION :
Wrong hints