Java根据权重按比例返回相应的值

左手的ㄟ右手 2022-07-13 07:49 490阅读 0赞

根据权重等比例返回相应的值，有很多种实现方式和途径。这里简单演示两种Java的程序实现，先贴代码：

public static void main(String[] args) throws ParseException {
            Map<String, Integer> map = new HashMap<>();
            map.put("A", 20);
            map.put("B", 10);
            map.put("C", 40);
            map.put("D", 30);
    
            //获取权重总和
            Integer sum = map.values().parallelStream().reduce(Integer::sum).get();
            //测试500W次
            Integer total = 5000000;
    
            //第一种方式
            int a = 0, b = 0, c = 0, d = 0;
            for (int i = 0; i < total; i++) {
                Integer random = new Random().nextInt(sum);
                for (String str : map.keySet()) {
                    int weight = map.get(str);
                    if (random > weight) {
                        random -= weight;
                    } else {
                        switch (str) {
                            case "A":
                                a++;
                                break;
                            case "B":
                                b++;
                                break;
                            case "C":
                                c++;
                                break;
                            case "D":
                                d++;
                                break;
                        }
                        break;
                    }
                }
            }
            System.out.println("第一种方式：");
            System.out.println("A:" + a + " 占比：" + ((float) a / total));
            System.out.println("B:" + b + " 占比：" + ((float) b / total));
            System.out.println("C:" + c + " 占比：" + ((float) c / total));
            System.out.println("D:" + d + " 占比：" + ((float) d / total));
    
            //第二种方式
            List<String> list = new ArrayList<>();
            map.keySet().forEach(key -> {
                int value = map.get(key);
                for (int i = 0; i < value; i++) {
                    list.add(key);
                }
            });
            Collections.shuffle(list);
            int A = 0, B = 0, C = 0, D = 0;
            for (int i = 0; i < total; i++) {
                String str = list.get(new Random().nextInt(sum));
                switch (str) {
                    case "A":
                        A++;
                        break;
                    case "B":
                        B++;
                        break;
                    case "C":
                        C++;
                        break;
                    case "D":
                        D++;
                        break;
                }
            }
            System.out.println("\n第二种方式：");
            System.out.println("A:" + A + " 占比：" + ((float) A / total));
            System.out.println("B:" + B + " 占比：" + ((float) B / total));
            System.out.println("C:" + C + " 占比：" + ((float) C / total));
            System.out.println("D:" + D + " 占比：" + ((float) D / total));
        }

实验结果：  
![这里写图片描述][SouthEast]

根据结果可以看出，两种方式都能满足要求。但相对而言，第一种方式更能省内存。

[SouthEast]: /images/20220713/561674def8e242c49649881261bcf02e.png