如何根据频率输出ArrayList的元素？

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import java.util.Collections;
import java.util.Comparator;

public class FrequencySort {
    public static List<Integer> sortByFrequency(List<Integer> inputList) {
        // Step 1: 统计频率
        Map<Integer, Integer> frequencyMap = new HashMap<>();
        for (int num : inputList) {
            frequencyMap.put(num, frequencyMap.getOrDefault(num, 0) + 1);
        }

        // Step 2: 按照频率排序
        List<Map.Entry<Integer, Integer>> entryList = new ArrayList<>(frequencyMap.entrySet());
        Collections.sort(entryList, new Comparator<Map.Entry<Integer, Integer>>() {
            public int compare(Map.Entry<Integer, Integer> entry1, Map.Entry<Integer, Integer> entry2) {
                return entry2.getValue().compareTo(entry1.getValue());
            }
        });

        // Step 3: 构建结果列表
        List<Integer> resultList = new ArrayList<>();
        for (Map.Entry<Integer, Integer> entry : entryList) {
            int num = entry.getKey();
            int frequency = entry.getValue();
            for (int i = 0; i < frequency; i++) {
                resultList.add(num);
            }
        }

        return resultList;
    }

    public static void main(String[] args) {
        List<Integer> inputList = new ArrayList<>();
        inputList.add(1);
        inputList.add(2);
        inputList.add(2);
        inputList.add(3);
        inputList.add(3);
        inputList.add(3);

        List<Integer> sortedList = sortByFrequency(inputList);
        System.out.println(sortedList);  // 输出 [3, 3, 3, 2, 2, 1]
    }
}