AP classes and joining one of the U.S service academies?

Yes and no. Technically, AP classes don't get you college credit for the service academies, but you can take a test to "validate" them, so you don't have to take them. But for some (at least at USNA) you can get out of taking a couple classes if you get at least a certain score. If you auto-validate a lot plus validate a lot from scoring high on the validation test(s), then you could take higher classes than what other Plebes/Doolies/whatever freshmen are called at the academy of your choice are taking. That opens up special things (liking working on a graduate degree) your senior year.

http://www.usna.edu/acdean/candidateinfo/USNACours... AP English you can take a test or if you get a 5 on the AP exam, it auto-validates.

Not exactly, instead of making life a little easier, that will just mean taking more advanced classes in their place. Most Mids/Cadets who have not been recruited for athletics or other academy goals and who have not spent a year at the service academy Prep School will have taken multiple AP courses including AP English Lit/Language, AP Calc, AP Chem/Physics with high AP Exam scores and around 700 minimum Sat Cr + Math scores. If a Cadet/Mid does not want a course to auto validate, be sure not to have the AP Exam scores forwarded to the service academy. For AP classes taken Senior year can also refrain from taking the AP Exam, though some high schools force students in AP classes to take the exams.

Well each Academy I would assume has different policies with AP credits and what they accept for it, as do all colleges.

Like I took AP world history, and my college would not offer me credit for because its just one of the AP classes they don't transfer from.

You will always take classes in a semester, you just will have more credits and possibly take a higher level course.

Like the Air Force Academy says their policy is:

The Air Force Academy will accept scores of four and five on most AP exams in conjunction with core course placement exams that you will take during Basic Cadet Training (BCT).

You take whatever is required for the Academy. AP classes don't necessarily replace college courses. You get out of nothing.

Just take as many AP's as possible.

nope