public class MySQL { final String JDBC_DRIVER = "com.mysql.cj.jdbc.Driver"; final String DB_URL = "jdbc:mysql://localhost:3306/student_message?serverTimezone=UTC&characterEncoding=utf-8"; final String USER = "root"; final…
一元操作符 表达式 对应的函数 +a a.unaryPlus() -a a.unaryMinus() !a a.not() a++ a.inc() a-- a.dec() fun main(arg: Array<String>) { var a = "a" println(a++) println(a) println(++a) } operator fun String.inc():String{//重载String的++ return this +this } 二元操作…