关于HashMap中的扰动函数的疑问

import com.alibaba.fastjson.JSON;

        import java.util.ArrayList;
        import java.util.Random;
        import java.util.List;

/**
 * @description:
 * @author: wukong
 * @remark: create wukong 2019/12/26 22:49
 */
public class HashTest {
    public static void main(String[] args) {
        int length = 1 << 8;
        List<Double> doubles = new ArrayList<>(100);
        List<Double> double2s = new ArrayList<>(100);
        // 测试次数
        int count = 100;
        for (int i = 0; i < count; i++) {
            hashCalculate(length, doubles, double2s);
        }
        System.out.println("均值1：" + doubles.stream().mapToDouble((item) -> item).summaryStatistics().getAverage());
        System.out.println("均值2：" + double2s.stream().mapToDouble((item) -> item).summaryStatistics().getAverage());
        System.out.println("集合1：" + JSON.toJSON(doubles));
        System.out.println("集合2" + JSON.toJSON(double2s));
    }

    /**
     * @Description: hash碰撞率计算
     */
    private static void hashCalculate(int length, List<Double> doubles, List<Double> double2s) {
        int cardinal = length - 1;
        int load = (int) (length * 0.75);
        int crash = 0;
        int crash2 = 0;
        List<Integer> list = new ArrayList<>();
        List<Integer> list2 = new ArrayList<>();
        for (int i = 0; i < load; i++) {
            // 随机key获取哈希值
            int hash = getRandomString().hashCode();
            // 直接与基数进行与运算
            int result = cardinal & hash;
            // jdk8中hashmap扰动函数
            int disturbHash = hash ^ (hash >>> 16);
            // 扰动后的值与运算
            int result2 = cardinal & disturbHash;
            //统计直接运算碰撞次数
            if (!list.contains(result)) {
                list.add(result);
            } else {
                crash++;
            }
            //统计扰乱后碰撞次数
            if (!list2.contains(result2)) {
                list2.add(result2);
            } else {
                crash2++;
            }
        }
        double crashProbability = crash / (double) length;
        double crashProbability2 = crash2 / (double) length;
        doubles.add(crashProbability);
        double2s.add(crashProbability2);
//      System.out.println("当长度为" + length + "时，hash值直接与运算的碰撞率为：" + crashProbability);
//      System.out.println("当长度为" + length + "时，扰动函数之后与运算的碰撞率为：" + crashProbability2);
    }

    /**
     * @Description: 获取随机key字符串
     */
    private static String getRandomString() {
        String str = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
        Random random = new Random();
        StringBuffer sb = new StringBuffer();
        int length = 8;
        for (int i = 0; i < length; i++) {
            int number = random.nextInt(62);
            sb.append(str.charAt(number));
        }
        return sb.toString();
    }
}