J. Swift was a 24th century Human. This person was the captain of the USS Yosemite.
In 2370, Capt. J. Swift was listed on the Deep Space 9 arrival roster. (DS9: "Whispers", production art)
This character was never mentioned or shown, it was simply listed in an okudagram graphic of an arrival roster on a viewscreen. The graphic was also populated by some other in-jokes. He was named for Jonathan Swift, famous Irish writer and satirist.