概述

用Java的Math.random()方法生成随机数。此方法为真随机。

代码

    public static void main(String[] args) {
        int size = 100;
        int cycle = 1000000;
        int count = 0;
        int target = 1;
        for(int i = 0; i < cycle; i++){
            int r = (int) (Math.random() * size);
            if(r == target){
                count++;
            }
        }
        System.out.println((((double) count/cycle) * 100) + "%");
    }

输出是1.0052%

验证真随机

    public static void main(String[] args) {
        int size = 10;
        int cycle = 1000000;
        int count = 0;
        int target = 1;
        int[] counts = new int[size];
        for(int i = 0; i < cycle; i++){
            int r = (int) (Math.random() * size);
            counts[r]++;
        }

        for (int i = 0; i < counts.length; i++) {
            System.out.println(i + "出现的概率：" + (double) counts[i]/cycle);
        }
    }

输出结果

从结果可以看出每个元素出现的概览相同。