看代码总能遇到关键字--type，对于type的概念不明白。翻译水平也有限，所以贴几个地址。自己先看着。
https://stackoverflow.com/questions/16600750/difference-between-class-and-type
https://docs.oracle.com/javase/specs/jls/se10/html/jls-4.html#jls-4.1