package mit_plugin;

import java.awt.BorderLayout;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.text.NumberFormat;

import javax.swing.JButton;
import javax.swing.JLabel;
import javax.swing.JTextPane;

import javax.swing.WindowConstants;
import javax.swing.SwingUtilities;

/**
 * This code was edited or generated using CloudGarden's Jigloo SWT/Swing GUI
 * Builder, which is free for non-commercial use. If Jigloo is being used
 * commercially (ie, by a corporation, company or business for any purpose
 * whatever) then you should purchase a license for each developer using Jigloo.
 * Please visit www.cloudgarden.com for details. Use of Jigloo implies
 * acceptance of these licensing terms. A COMMERCIAL LICENSE HAS NOT BEEN
 * PURCHASED FOR THIS MACHINE, SO JIGLOO OR THIS CODE CANNOT BE USED LEGALLY FOR
 * ANY CORPORATE OR COMMERCIAL PURPOSE.
 */
public class GUI_plugin extends javax.swing.JFrame {
	private JTextPane textfield_dm;;
	private JButton jButton;
	private JLabel jLabel2;
	private JLabel jLabel1;
	private JTextPane textfield_euro;;

	/**
	 * Auto-generated main method to display this JFrame
	 */
	public static void main(String[] args) {
		SwingUtilities.invokeLater(new Runnable() {
			public void run() {
				GUI_plugin inst = new GUI_plugin();
				inst.setLocationRelativeTo(null);
				inst.setVisible(true);
			}
		});
	}

	public GUI_plugin() {
		super();
		initGUI();
	}

	private void initGUI() {
		try {
			setDefaultCloseOperation(WindowConstants.DISPOSE_ON_CLOSE);
			getContentPane().setLayout(null);
			{
				textfield_dm = new JTextPane();
				getContentPane().add(textfield_dm);
				textfield_dm.setBounds(45, 49, 127, 31);
			}
			{
				textfield_euro = new JTextPane();
				getContentPane().add(textfield_euro);
				textfield_euro.setBounds(233, 49, 127, 31);
			}
			{
				jLabel1 = new JLabel();
				getContentPane().add(jLabel1);
				jLabel1.setText("DM");
				jLabel1.setBounds(45, 24, 35, 14);
			}
			{
				jLabel2 = new JLabel();
				getContentPane().add(jLabel2);
				jLabel2.setText("Euro");
				jLabel2.setBounds(233, 24, 33, 14);
			}
			{
				jButton = new JButton();
				getContentPane().add(jButton);
				jButton.setText("Umwandlung von DM in Euro");
				jButton.setBounds(212, 123, 203, 42);
				jButton.addActionListener(new ActionListener() {
					public void actionPerformed(ActionEvent evt) {
						System.out.println("jButton.actionPerformed, event="
								+ evt);
						// TODO add your code for jButton.actionPerformed
						buttonBerechneClicked();
					}
				});
			}
			pack();
			this.setSize(457, 332);
		} catch (Exception e) {
			e.printStackTrace();
		}
	}

	// Die Methode für die Aktion, wenn der Knopf gedrückt wird
	public void buttonBerechneClicked() {
		double dm = 0;
		try {
			// Den DM-Wert aus dem Fenster ziehen
			dm = Double.parseDouble(textfield_dm.getText());
		} catch (NumberFormatException e) {
			dm = -1;
		}
		if (dm >= 0) {
			// in Euro umrechnen
			double euro = dm2euro(dm);
			// Für die Stringvariable ausgabe formatieren
			NumberFormat nf = NumberFormat.getInstance();
			nf.setMaximumFractionDigits(2);
			String ausgabe = nf.format(euro) + "€";
			textfield_euro.setText(ausgabe);

		} else
			textfield_euro.setText("Fehler in der Eingabe");

	}

	// Die Methode für die eigentliche Umrechnung
	public double dm2euro(double dm) {
		double euro = dm / 1.95583;
		return euro;
	}

}

Vgl auch die Synopse der Quelltexte.