toJSONStringWithDateFormat uses

1. By comparing normal conversions with conversions with time

    public static void main(String[] args) {
        List<Map<String ,Object>> list = new ArrayList();
        Map<String ,Object> map = new HashMap<>();
        Person p = new Person("张三", "女", new Date());
        map.put("1", p);
        Person p1 = new Person("李四", "男", new Date());
        map.put("2", p1);
        list.add(map);
        String s = JSONObject.toJSONString(list);
        String s1 = JSONObject.toJSONStringWithDateFormat(list, JSON.DEFFAULT_DATE_FORMAT);
        System.out.println("s执行结果: "+s);
        System.out.println("s1执行结果: "+s1);
    }

Created Person class

public class Person implements Serializable {

    private String name;

    private String sex;

    private Date date;

    public Person(String name, String sex, Date date) {
        this.name = name;
        this.sex = sex;
        this.date = date;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getSex() {
        return sex;
    }

    public void setSex(String sex) {
        this.sex = sex;
    }
}

2. Results of the

s执行结果: [{"1":{"date":1672990998981,"name":"张三","sex":"女"},"2":{"date":1672990998981,"name":"李四","sex":"男"}}]
s1执行结果: [{"1":{"date":"2023-01-06 15:43:18","name":"张三","sex":"女"},"2":{"date":"2023-01-06 15:43:18","name":"李四","sex":"男"}}]

3. Conclusion
   It is easy to see from the comparison results that this method can convert time into a readable String.

4. 
   Import this dependency in maven using prerequisites

   <dependency>
       <groupId>com.alibaba</groupId>
       <artifactId>fastjson</artifactId>
       <version>1.2.60</version>
   </dependency>