Android开发(Java部分)——Map基本使用

Map接口 映射 没有顺序
   -|HashMap 管理键值对
   -|ConcurrentMap 线程安全
   -|LinkedHashMap

key：键
value：值

MyClass.java

class Person{
    int age;
    int score;
    String name;

    public Person (int age, int score, String name) {
        this.age = age;
        this.score = score;
        this.name = name;
    }

    @Override
    public String toString() {
        return "Person" +
            "age=" + age +;
    }
}


public class MyClass {
    public static void main(String[] agrs) {
        Map<String, Person> map = new HashMap<>();

        //添加一个键值对
        map.put(k: "jack", new Person(age: 30, score: 98, name: "jack"));
        map.put(k: "merry", new Person(age: 32, score: 62, name: "merry"));

        //获取键值对的个数
        System.out.println(map.size());

        //是否包含某一个key
        System.out.println(map.containsKey(o: "jack232"));//false
        
        //判断是否包含某个value
        System.out.println(map.containsValue(person));

        //获取某个key对应的value
        Person p = map.get("jack");
        System.out.println("jack:"+p);//jack:person{age=30, score=98, name='jack'}
        
        //删除某个键值对
        map.remove(o: "jack");

        //替换某个键值对
        map.replace(k: "jack", new Person(age: 32, score: 32, name: "张三"));
        System.out.println(map);//jack=Person{age=32, score=32, name='张三'}

        //清空
        map.claer();
        
        //map遍历
        Set<Map.Entry<String, Person>> entries = map.entrySet();
        for (Map.Entry<String, Person> entry: entries){
            System.out.println("key:"+entry.getKey()+" value:"+entry.getValue());
        }
        
    }