Window.scala

import java.awt._
import javax.swing._
class Window(t: String,frash:FrashCard) extends JFrame(t){

	val frashCard = frash
	val panel:JPanel = new JPanel(new GridLayout(1,1))

	val tit = t
	makeWindow();
	add(panel)

	def this() = this("FrashCard",new FrashCard)


	def makeWindow(){
		setSize(500,500)
		setTitle(tit)
		setLayout(new GridLayout)

		setLocationRelativeTo(null);
		setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE)
		addMouseListener(
		    new MouseListener{
		      def mouseClicked(event:MouseEvent){
		    	  addString (frashCard goNext)
		      }
		      def mousePressed(event:MouseEvent){}
		      def mouseReleased(event:MouseEvent){}
		      def mouseEntered(event:MouseEvent){}
		      def mouseExited(event:MouseEvent){}
		    }
		)
		println("Window made!")
	}
	def addString(word:String){
	  println("called! " + word)
	  panel.add(new JLabel(word))
	  repaint()
	  println("repainted")
	}

}

なるほど。ありがとうございます！じつはどうも描画がおかしい、と他の方から相談があったソースコードなので、FrashCardについてはその方に聞いてみます。
ありがとうございます！