Java 数组随机打乱顺序

random.java

public static void shuffle(Object[] a) {
    //判断数组 a 是否可以转为整型数组 
    validateNotNull(a);
    int n = a.length;
    for (int i = 0; i < n; i++) {
        int r = i + uniform(n-i);     // between i and n-1
        Object temp = a[i];
        a[i] = a[r];
        a[r] = temp;
    }
}

public static int uniform(int n) {
    if (n <= 0) throw new IllegalArgumentException("argument must be positive: " + n);
    return random.nextInt(n);
}