Given tries & confidence (1-risk), calculate success (1-failure)

dropChance.java

/**
* Given tries & confidence (1-risk), calculate success (1-failure) 
*  failure = risk^(1/tries)
*  success = 1 - (1-confidence)^(1/tries)
* @param tries before it's confidence% certain the loot has dropped
*/
double calcDropChance(int tries){
  return 1.0 - Math.pow(1.0 - confidence, 1.0 / tries);
}