travelling to the USA on a J-1 visa, do i require to book a return flight?

im thinking of travelling for a bit out there after the study period is over, and not sure when i will be returning. Is it by US law that i need to book a return flight or can i book one way and book the return flight at a later date when im out there?

Contact the US Embassy or Consulate (General) ; they can give you precise information.

See site below and read what it says under,"How long am I permitted to sty in the U.S. after my exchange period has ended?" it says you have 30 days, then must leave. There is also info on how to request an extension.