public class RateAlgorithm { public static void main(String[] args) { int index0 = 0; int index1 = 0; int index2 = 0; int index3 = 0; //Get the probability list of items double rateA[] = { 0.1, 0.2, 0.3, 0.4 }; for (int k = 0; k < 1000; k++) { // int index = rateAlgor1(rateA); int index = rateAlgor2(rateA); if (index == 0) { index0++; } else if (index == 1) { index1++; } else if (index == 2) { index2++; } else if (index == 3) { index3++; } } System.out.println("index0=" + index0 + ",index1=" + index1 + ",index2=" + index2 + ",index3=" + index3); } /** *Probability algorithm 1 * * @param rateA *Probability List * @return */ private static int rateAlgor1(double rateA[]) { double random = new Random().nextDouble(); for (int i = 0; i < rateA.length; i++) { if (random <= getRate(rateA, i)) { return i; } } return rateA.length; } private static double getRate(double rateA[], int index) { double rate = 0; for (int j = 0; j < rateA.length; j++) { if (j <= index) { rate += rateA[j]; } } return rate; } /** *Probability algorithm 2 * * @param rateA *Probability List * @return */ private static int rateAlgor2(double rateA[]) { double random = new Random().nextDouble(); for (int i = 0; i < rateA.length; i++) { if (random <= rateA[i]) { return i; } random -= rateA[i]; } return rateA.length; } }
