Archief - [PROG]-[JAVA] Applet not initialized

import java.awt.*;
import java.applet.*;
import java.awt.event.*;

public class eind_oefening extends Applet
{
	TextField invoer, getal1, getal2, uitvoer;
	Label van, tot;
	Button knopje;
	
	public void init()
	{
		invoer = new TextField("aardappelsalade",15);
		invoer.setEditable(false);
		
		getal1 = new TextField("",10);
		
		getal2 = new TextField("",10);
		
		van = new Label("van");
		
		tot = new Label("tot");
		
		knopje = new Button("OK");
		knopje.addActionListener(new KnopHandler());
		
		// toevoegen van alles
		
		add(invoer);
		add(van);
		add(getal1);
		add(tot);
		add(getal2);
		add(knopje);
		add(uitvoer);
		
	}
	
	class KnopHandler implements ActionListener
	{
		public void actionPerformed(ActionEvent e)
		{
			String splits;
			String woord = invoer.getText();
			
			String invoer1 = getal1.getText();
			int getal1 = Integer.parseInt(invoer1);
			
			String invoer2 = getal2.getText();
			int getal2 = Integer.parseInt(invoer2);
			
			splits = woord.substring(getal1,getal2);
			
			uitvoer.setText(splits);
			
		}
	}
}

java.lang.NullPointerException
	at java.awt.Container.addImpl(Unknown Source)
	at java.awt.Container.add(Unknown Source)
	at eind_oefening.init(eind_oefening.java:35)
	at sun.applet.AppletPanel.run(Unknown Source)
	at java.lang.Thread.run(Unknown Source)
Exception in thread "thread applet-eind_oefening.class" java.lang.NullPointerException
	at sun.plugin.util.GrayBoxPainter.showLoadingError(Unknown Source)
	at sun.plugin.AppletViewer.showAppletException(Unknown Source)
	at sun.applet.AppletPanel.run(Unknown Source)
	at java.lang.Thread.run(Unknown Source)

uitvoer = new TextField("",15);