求写下代码，并每行添加注释

Question

/*
请用代码将list2中的score合并到List中(如果匹配不到则用"-"代替)
*/
package test;

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

public class Exercise {

public static void main(String[] args) {
    List<Map<String,String>> list1=new ArrayList<>();
    List<Map<String,String>> list2=new ArrayList<>();
    Map<String,String>map;

    map=new HashMap<>();
    map.put("id","1");
    map.put("name","张三");
    list1.add(map);

    map=new HashMap<>();
    map.put("id","2");
    map.put("name","李四");
    list1.add(map);

    map=new HashMap<>();
    map.put("id","3");
    map.put("name","王五");
    list1.add(map);

    map=new HashMap<>();
    map.put("id","2");
    map.put("score","90");
    list2.add(map);

    map=new HashMap<>();
    map.put("id","3");
    map.put("score","88");
    list2.add(map);

    map=new HashMap<>();
    map.put("id","4");
    map.put("score","75");
    list2.add(map);

    //todo 从这里开始
}

}

Answer 1

我是这样理解题干的，如果list1里面的id和list2里面的id相同，则更新list1里面的score，代码如下，时间仓促，写的有点着急：

 public static void main(String[] args) {
        List<Map<String,String>> list1=new ArrayList<>();
        List<Map<String,String>> list2=new ArrayList<>();
        Map<String,String>map;
        map=new HashMap<>();
        map.put("id","1");
        map.put("name","张三");
        list1.add(map);
        map=new HashMap<>();
        map.put("id","2");
        map.put("name","李四");
        list1.add(map);
        map=new HashMap<>();
        map.put("id","3");
        map.put("name","王五");
        list1.add(map);
        map=new HashMap<>();
        map.put("id","2");
        map.put("score","90");
        list2.add(map);
        map=new HashMap<>();
        map.put("id","3");
        map.put("score","88");
        list2.add(map);
        map=new HashMap<>();
        map.put("id","4");
        map.put("score","75");
        list2.add(map);
        //todo 从这里开始

        for(Map<String,String> map1:list1){
            for(Map.Entry<String, String> entry1:map1.entrySet()){
                if ("id".equals(entry1.getKey())){
                    boolean bool=false;
                    String score="";
                    for (Map<String,String> map2:list2){
                        for(Map.Entry<String, String> entry:map2.entrySet()){
                            if ("id".equals(entry.getKey()) && entry1.getValue().equals(entry.getValue())){
                                bool=true;
                            }
                        }
                        if (bool){
                            score = map2.get("score");
                            break;
                        }else{
                            score="-";
                        }
                    }
                    map1.put("score",score);
                }
            }
        }
        list1.forEach(l->{
            System.out.println("===================================>");
            l.forEach((k,v)->{
                System.out.println("k:"+k+",v:"+v);
            });
            System.out.println("===================================>");
        });
    }

打印list1集合结果如下：