package com.example.news.models class user( val username: string, val email: string, val gender: string ) { // 如果需要默认构造函数，可以添加 constructor() : this("", "", "") }和package com.example.news.models import java.io.serializable class news( val title: string, val content: string, val publisher: string, val publishtime: string = java.util.date().tostring() ) : serializable { }和package com.example.news.models data class comment( val content: string, val com