特质->self type:this

 trait Buffering {   this: FileInputStream =>   val b = new BufferedInputStream(this)   override def read(ab: Array[Byte]): Int = {     b.read(ab)   } } val b = new FileInputStream("c:/ObjectTest.obj") with Buffering val ab = new Array[Byte](10) while(b.read(ab) != -1) {  ab.foreach(a => print(a.toChar))}