Why does minecraft lag when I have a gaming computer that should be able to run it fine?

I don't understand why minecraft lags so much when I can run games like battlefield hardline, planetside 2 and tf2 all at max settings just fine. On about a little above medium settings in minecraft I only get about 45fps. But yet I can max other games and still get better frame rates. I don't understand it I have heard so many people say how minecraft doesn't take much to run yet it's one of the few games I'm having problems with. I also have kind of low fps on DayZ but I can understand as that is a more demanding game.

My specs:
fx 8320
8gb ram
PowerColor r9 280
1tb harddrive
750w psu