scala1. ``` package level1.class1 import level1.class1

package level1.class1

import level1.class1.scala2.MyTool

object scala2 {
object MyTool
  val PI = 3.14
  def Area（r:Double):Double = {
    PI * r * r
  }
}

def main(args: Array[String]): Unit = {
  println( MyTool.PI)
  println(MyTool.Area(10))
}

package level1.class1

class scala3 {
class Student() {
  private  val hobby = "打游戏"
  object Student {
    def introduce(stu: Student): Unit = {
      println(s"我的爱好是：￥{stu.hobby}")
    }
  }

  def main(args: Array[String]): Unit = {
    val stu1 = new Student()
      Student.introduce(stu1)

  }
}
}

package level1.class1

object scala4 {
  class Logger(var filename: String) {

  }
  object Logger {
    def apply(filename:String):Logger = {
      println("apply...")
      new Logger(filename)
    }
  }

  def main(args: Array[String]): Unit = {
    val log1 = Logger("test.log")
    println( log1.filename)
  }

}