JAVA Gson的使用

<dependency>
          <groupId>com.google.code.gson</groupId>
          <artifactId>gson</artifactId>
          <version>2.8.2</version>
</dependency>

import com.google.gson.Gson;
import com.google.gson.GsonBuilder;
import com.google.gson.reflect.TypeToken;
import com.sun.scenario.effect.impl.sw.sse.SSEBlend_SRC_OUTPeer;
import java.time.LocalDateTime;
import java.time.format.DateTimeFormatter;
import java.util.*;
import static jdk.nashorn.internal.objects.Global.print;
/**
 * @Author : JCccc
 * @CreateTime : 2018-11-27
 * @Description :
 * @Point: Keep a good mood
 **/
public class testMain {
    public static void main(String[] args) {
     //手动创的一个实体类， 里面字段全是String类型
        User userTest=new User();
        userTest.setName("joke");
        userTest.setAge("16岁");
        userTest.setHeight("60Kg");
        userTest.setSex("男");
        Gson gson=new Gson();
        String jsonStr=gson.toJson(userTest,User.class);
        System.out.println("对象转JSON---"+jsonStr);
        User userTestNew=gson.fromJson(jsonStr,User.class);
        System.out.println("JSON转对象---"+userTestNew.toString());
       Map map=new LinkedHashMap();
       map.put("name","merry");
       map.put("age","17岁");
       map.put("height","62Kg");
       map.put("sex","女");
       String mapJsonStr=gson.toJson(map);
        System.out.println("map转JSON---"+mapJsonStr);
        List<User> userList = new ArrayList<>();
        userList.add(userTest);
       // System.out.println(userList.toString());
        String listJsonStr=gson.toJson(userList);
        System.out.println("list转JSON---"+listJsonStr);
        List<User> retList = gson.fromJson(listJsonStr,new TypeToken<List<User>>(){}.getType());
        System.out.println("listJSON转list---"+retList);
//报错
//        List<User> retList1 = gson.fromJson(mapJsonStr,new TypeToken<List<User>>(){}.getType());
//        System.out.println("mapJSON转list---"+retList1);
//报错
        /*List<User> retList2 = gson.fromJson(jsonStr,new TypeToken<List<User>>(){}.getType());
        System.out.println("对象JSON转list---"+retList2);*/
    }
}