Java interop errata

There are a few possibilities for improvement on this Scala Swing Example.

• Removed unnecessary semi-colons
• Inlined import
• Removed = in main declaration (strongly advised on functions returning Unit and especially more for main)
• Removed a few unnecessary parentheses

import javax.swing._
import java.awt.event.{ActionEvent, ActionListener}

object HelloWorld extends JFrame("Hello Swing") {
  def showButtonMessage(msg: String)  =
    JOptionPane.showMessageDialog(null, String.format("""Hello from Scala. Button %s pressed""", Array(msg)));

  def main(args: Array[String]) {
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE)
    val button = new JButton("Click Me")
    button.addActionListener((e:ActionEvent) => showButtonMessage(e.getActionCommand.toString))
    getContentPane add button
    pack
    setVisible(true)
  }

  implicit def actionPerformedWrapper(func: (ActionEvent) => Unit) = new ActionListener {
    def actionPerformed(e:ActionEvent) = func(e)
  }
}