GA中的轮盘赌轮选择：ArrayIndexOutOfBoundsException错误

Question

基于this answer我试图在遗传算法中选择轮盘赌。

private static final int NUMBER_OF_TOURISTS = 20;

private static int[] roulette(int population[]) {
    int sumProb = 0;
    for (int i = 0; i < population.length; i++) {
        sumProb += population[i];
    }

    int[] rouletteIndex = new int[NUMBER_OF_TOURISTS];
    Random r = new Random();
    for (int i = 0; i < NUMBER_OF_TOURISTS; i++) {
        int numberRand = r.nextInt(sumProb);
//-------------------------------------------------------
        int j = 0;          
        while (numberRand > 0) {
            numberRand = numberRand - population[j];
            j++;
        }
        rouletteIndex[i] = j-1;
//-------------------------------------------------------
    }
    return rouletteIndex;
}

之后我得到：

[6, 2, -1, 19, 13, 2, 14, 2, 6, 19, 7, 14, 18, 0, 1, 9, 13, 10, 7, 2]

“ - 1”？但是，当j应该总是大于0时如何。 当numberRand = 0并且while循环甚至没有启动一次时会发生这种情况吗？但是如何解决这个问题？

Answer 1

Random.nextInt(int bound)返回0（含）到指定的边界（不包括）。

所以你的循环：

while (numberRand > 0) {
    numberRand = numberRand - population[j];
    j++;
}

如果nextInt(int bound)返回0，则无法运行，导致j为0：rouletteIndex[i] = j-1;