java-web - java map排序

Question

需求是这样的：

现在有一个list，里面n个map，每个map都有m大小的key-value，且每个map的key的顺序都是一样的，比如说map1的第x个key是y，那么mapn的第x个key也是y。

现在要对list中的每个map进行排序，要按n个map中的相同的key的value值的和的顺序排序。

举例：比如3个map，都有key1,key2，如果
map1.get(key2) + map2.get(key2) + map3.get(key2) > map1.get(key1) + map2.get(key1) + map3.get(key1),
那么就要将这三个map中的key的顺序按照key2,key1的顺序排列，原先每个map中key的顺序是key1,key2。

怎么来实现呢

Answer 1

1. First calculate the sorting of the sum of all keys
2. Traverse the original list, according to the order corresponding to the key, and then put it into a list

List<String> sortedKeys = ...; // 第一步算的结果
List<Map<String, Integer>> originList = ...; // 原始数据集合
List<Map<String, Integer>> resultList = new ArrayList<Map<String, Integer>>();

for(Map<String,Integer> originMap : originList) {
    Map<String, Integer> sortedMap = new LinkedHashMap<String, Integer>();
    for(String sortedKey : sortedKeys) {
        sortedMap.put(sortedKey, originMap.get(sortedKey));
    }
    resultList.put(sortedMap);
}

Answer 2

Ordered Map can be achieved with TreeMap, so I use java.util.TreeMap in the example.

Generally SortedMap can use a Comparator as a construction parameter, then you can write a Comparator yourself to implement sorting. The following is an example

import java.util.*;

public class Test {
    private SortedMap<String, Integer> first;
    private SortedMap<String, Integer> second;
    private SortedMap<String, Integer> third;
    private SortedMap<String, String> main;

    public Test() {
        first = new TreeMap<String, Integer>();
        second = new TreeMap<String, Integer>();
        third = new TreeMap<String, Integer>();
        main = new TreeMap<String, String>(new Comparator<String>() {
            public int compare(String k1, String k2) {
                Integer v1 = first.get(k1) + second.get(k1) + third.get(k1);
                Integer v2 = first.get(k2) + second.get(k2) + third.get(k2);
                return v2 - v1;
            }
        });
    }

    public void put(String key, String value, Integer v1, Integer v2, Integer v3) {
        first.put(key, v1);
        second.put(key, v2);
        third.put(key, v3);
        main.put(key, value);
    }

    public SortedMap<String, String> getMain() {
        return main;
    }

    public static void main(String[] args) {
        Test test = new Test();
        test.put("a", "aaaaaaaa", 1, 2, 3);
        test.put("b", "bbbbbbbb", 10, 20, 30);
        test.put("c", "cccccccc", 5, 15, 20);
        test.put("d", "dddddddd", 100, 1, 3);

        for (Map.Entry<String, String> entry : test.getMain().entrySet()) {
            System.out.println(entry.getKey() + " : " + entry.getValue());
        }
    }
}