如何根据Map中的Integer值相对于O(n)时间内的其他值随机选择一个键？

import java.util.*;

public class RandomKeySelector {
    public static void main(String[] args) {
        Map<String, Integer> map = new HashMap<>();
        map.put("A", 10);
        map.put("B", 20);
        map.put("C", 30);
        map.put("D", 40);

        String selectedKey = selectRandomKeyByValue(map);
        System.out.println("Selected key: " + selectedKey);
    }

    public static String selectRandomKeyByValue(Map<String, Integer> map) {
        int totalSum = 0;
        for (int value : map.values()) {
            totalSum += value;
        }

        Random random = new Random();
        int randomValue = random.nextInt(totalSum);

        int currentSum = 0;
        for (Map.Entry<String, Integer> entry : map.entrySet()) {
            currentSum += entry.getValue();
            if (currentSum >= randomValue) {
                return entry.getKey();
            }
        }

        return null;
    }
}