定义 class trait object 产生类型

type关键字 声明类型 声明别名(alias)

type S = String
defined type alias S

val str:S = "hello"
str: S = hello
val str2 = str + " world"
str2: String = hello world

package object scala {
  type Throwable = java.lang.Throwable
  type Exception = java.lang.Exception
  type Error     = java.lang.Error


val e:scala.Exception = new Exception("error")
e: Exception = java.lang.Exception: error



 scala 包对象 package object