Mini Java Interpreter Lab 2 and 3

This is my Lab 2/3 code of the Nanjing University course Interpreters and Virtual Machines of Programming Languages in Kotlin. 这是南京大学课程“程序设计语言的解释器和虚拟机”Lab2/3我的示例代码，使用Kotlin编写。

Note that the code has been completely rewritten compared to Lab1 注意相较Lab1代码已经完全重写

main holds the code of completed lab 3. You can visit the tag lab 2 to visit lab 2 code. main分支是Lab3完成的代码。Lab2的代码请看标签。