I use some giant loops in java, so i made few speed tests, just wanted to share them:

// CALCULATIONS IN JAVA – SPEED TESTS :
//
// OK in giant loops…
// assignment: ~ 1-5 cycles
// addition/substraction: ~ 1-5 cycles
// multiplication: ~ 3-6 cycles
//
// Not so ok… division: ~ 10-20 cycles
//
// Not ok at all…
// Math.pow(…,1 or 2): ~ 55 cycles
// Math.exp: ~ 75 cycles
// Math.log: ~ 95 cycles
// Math.random: ~ 120 cycles
// Math.pow(…,anything): ~ 460 cycles !
// Math.pow(…,0.5): ~ 720 cycles !!!

(Cycles of my I7 processor)

So after that, i made some look-up tables classes for this Math.stuff, 24 times faster than Math.pow, if you want them, just ask!