Why commercial planes dont use the f 119 engine ?

First, you can't just bolt an F119 engine onto an existing commercial airliner and expect it go supersonic. You have to design the whole airplane for supersonic flight. Second, the engine may be enough to propel a maximum take-off weight of 83,500 lb fighter (though I doubt that it will go supersonic at such heavy weight) but it won't be near enough for a long range commercial airliner. Just for a comparison, an F119 in full afterburner produces 35,000+ pounds of thrust. A GE90-115 on a 777 produces over 115,300 pounds of thrust. Three F119s will come up a little short of replacing a single GE-90. Third, comparing and F119 to a GE-90 is like comparing an engine for a Formula 1 car to that of a family sedan. A race car engine gets rebuilt after every race. With a family sedan, you're lucky if the owner changes oil every 5,000 miles. The F119 was designed for rapid acceleration and thrust vectoring at the expense of longevity. A normal operational tempo for a fighter involves flying about 200-300 hours per year. The GE-90 was designed to run for 18 hours at a time, every day. The technology developed for military engines does find its way into civilian programs and vice versa. The J52 engine from the Navy's EA-6 is nothing more than the JT8D we came to know and love on the Boeing 727/737 and DC-9/MD-80. The engine core of the CFM-56 was developed from the F-16's F110 engine.

Commercial jets already have their speeds limited to prevent sonic booms. It isn't that the planes can't go supersonic, they're just restricted from doing so. http://www.law.cornell.edu/cfr/text/14/91.817

The F-119 has an extremely high thrust-weight ratio. On the F-22, just 50% thrust makes a TW ratio of 1.26. That's a lot, but if you put, say, eight F-119s on a Boeing 737, it won't get past Mach 1, if it does make Mach 1. Compare the 737 and Concorde. The Concorde looks like an over-sized fighter jet. Swept-back wings don't work out too well for supersonic flight, while deltas are more suitable. Also, look at the 737's (or some other subsonic airliner) nose. It's blunt, like a Sharpie cap. Supersonic aircraft have noses that have a slight resemblance to fine-point Sharpie tips. Should your regular airliner be capable of mounting the F-119, it's not going to fly. The engines are just too powerful, so they'll either shoot the wings away or launch the engines into a fiery explosion.

Civilian supersonic jets are obsolete. Originally, they were meant to transport business heads to different parts of the world quickly to attend meetings and such. With teleconferencing and the rise of multinational corporations, meetings such as this are required very seldom - or not at all - in this day and age. The prohibitive cost to the passenger (a cost that used to be covered by businesses...) keeps it from being a means of flight to tourists and leisure travelers.

we can make supersonic airliners, and have done so. nobody wants them.

because the engines on commercial jets are powerful enough as it is and in most cases are too big for that engine

For the 10,000th time..... The marketplace does not need Supersonic airliners. Tech is not the issue. Noise, fuel & passenger volume is the issue.

The answer is "or what". It is not the lack of technology or unavailability of appropriate engines, it is simply a matter of economics. Supersonic flight is simply not efficient enough from a cost standpoint to make it viable for commercial purposes.

It's the wrong size. Engines are designed to meet the specific thrust and size requirements of an airplane design. Airplanes are not designed to use a particular engine. If an airplane was being designed that happened to need an engine with the characteristics of the F119 a commercial version would be developed.