java中Map接口常用的方法解读

 Map<Integer, String> map = new HashMap<>();
 map.put(1,"刘亦菲");
 map.put(2,"胡歌");
 map.put(3,"吴奇隆");
 map.put(4,"刘诗诗");
 map.put(5,"萧亚轩");
 System.out.println(map.values());

public class Woman {
        String name;
        Integer age;
        //其他省略。。。
    }  

import java.util.*;
public class MapTest {
    static Map<String, List<Woman>> map = new HashMap<>();
    public static void main(String[] args) {
        List<Woman> list = new ArrayList<>();
        list.add(new Woman("刘亦菲", 35));
        map.put("China", list);
        // 判断map中是否存在China，如果存在则添加元素到list中，如果不存在则新建list添加到map中
        if (map.containsKey("China")) {
            map.get("China").add(new Woman("刘诗诗", 25));
        } else {
            List<Woman> list2 = new ArrayList<>();
            list2.add(new Woman("刘诗诗", 25));
            map.put("China", list2);
        }
        System.out.println(map.toString());
    }
}

public class MapTest {
    static Map<String, List<Woman>> map = new HashMap<>();
    public static void main(String[] args) {
        List<Woman> list = new ArrayList<>();
        list.add(new Woman("刘亦菲", 35));
        map.put("China", list);
        // after JDK1.8
        map.computeIfAbsent("China", key -> getValues(key)).add(new Woman("刘诗诗", 25));
        System.out.println(map);
    }
    public static ArrayList getValues(String key) {
        return new ArrayList();
    }
}