import org.json4s.{Formats, NoTypeHints}import org.json4s.jackson.Serializationimport org.json4s.jackson.Serialization.writeobject Json4sDemo {    // 需要添加隐式转换    implicit val formats: AnyRef with Formats = Serialization.formats(NoTypeHints)    def main(args: Array[String]): Unit = {        val user1 = User(1, name = "李明", 12)        val user2 = User(2, name = "张杰", 43)        val user3 = User(3, name = "王伟", 54)        val user4 = User(4, name = "刘安", 24)        val users = List[User](user1, user2, user3, user4)        // 由scala 对象转换为 Json字符串        val str = write(user1)        println(str)        val sts = write(users)        println(sts)    }    case class User(id: Int, name: String, age: Int)}