Java Currency converter

Question

I am a beginning Java developer and I have a question regarding a little "tryout" applet I'm writing. This is my code so far:
//Applet 01 - Euro Converter - Build_001
import java.applet.*;
import java.awt.*;
public class Euro extends Applet
     TextField invoerbedrag;
     TextField koers;
     Button eurogulden;
     Button guldeneuro;
     Label uitvoer;
     String
     public void paint (Graphics pen)
          invoerbedrag.setBounds(100,30,100,25);
          koers.setBounds(250,30,100,25);
          eurogulden.setBounds(125,100,100,25);
          guldeneuro.setBounds(225,100,100,25);
          uitvoer.setBounds(150,150,100,25);
          pen.drawString("Invoer:",100,20);
          pen.drawString("Koers:",250,20);
          pen.setColor(Color.black);
     public void init()
          uitvoer=new Label("");
          add(uitvoer);
          invoerbedrag=new TextField("");
          add(invoerbedrag);
          koers=new TextField("2.20371");
          add(koers);
          eurogulden=new Button("Euro > Gulden");
          add(eurogulden);
          guldeneuro= new Button("Gulden > Euro");
          add(guldeneuro);
}It's all in Dutch, but it only is the layout. Now I have to make the number in the "invoer" textbox be dived by the number in the "koers"
textbox when I click on button "guldeneuro" and I have to make to number in the "invoer" textbox be multiplied by the number in the
"koers" textbox when I click on the button "eurogulden". The result of a click should be displayed in the "uitvoer" label. An other thing that is important is that the numbers could be both decimal and non decimal. Could someone write me a piece of code that does the job and explain me the working?
Thanks for your help.

Answer 1

Okay I have made some progress:
//Applet 01 - Euro Converter - Build_001
import java.applet.*;
import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
public class Euro extends Applet
     TextField invoer;
     TextField koers;
     Button eurogulden;
     Button guldeneuro;
     Label uitvoer;
     public void paint (Graphics pen)
          invoer.setBounds(100,30,100,25);
          koers.setBounds(250,30,100,25);
          eurogulden.setBounds(125,100,100,25);
          guldeneuro.setBounds(225,100,100,25);
          uitvoer.setBounds(150,150,100,25);
          pen.drawString("Invoer:",100,20);
          pen.drawString("Koers:",250,20);
          pen.setColor(Color.black);
     public void init()
          guldeneuro.addActionListener(this);
          eurogulden.addActionListener(this);
          uitvoer=new Label("");
          add(uitvoer);
          invoer=new TextField("");
          add(invoer);
          koers=new TextField("2.20371");
          add(koers);
          eurogulden=new Button("Euro > Gulden");
          add(eurogulden);
          guldeneuro=new Button("Gulden > Euro");
          add(guldeneuro);
     public void actionPerformed(ActionEvent actionevent)
          actionevent.getSource();
             String s = actionevent.getActionCommand();
            if(s.equals("Euro > Gulden"))
                if(invoer.getText() != "")
                    Double double1 = new Double(invoer.getText());
                    double d = double1.doubleValue() / koers.getText();
                    Double double3 = new Double(d);
                    uitvoer.setText(double3.toString());
                    return;
            } else
            if(s.equals("Gulden > Euro") && invoer.getText() != "")
                Double double2 = new Double(invoer.getText());
                double d1 = double2.doubleValue() * koers.getText();
                Double double4 = new Double(d1);
                uitvoer.setText(double4.toString());
}But when compiling I get some error's:
C:\Program Files\Java\Java Development Kit\bin\Euro.java:35: addActionListener(java.awt.event.ActionListener) in java.awt.Button cannot be applied to (Euro)
          guldeneuro.addActionListener(this);
          ^
C:\Program Files\Java\Java Development Kit\bin\Euro.java:36: addActionListener(java.awt.event.ActionListener) in java.awt.Button cannot be applied to (Euro)
          eurogulden.addActionListener(this);
          ^
C:\Program Files\Java\Java Development Kit\bin\Euro.java:64: operator / cannot be applied to double,java.lang.String
double d = double1.doubleValue() / koers.getText();
^
C:\Program Files\Java\Java Development Kit\bin\Euro.java:70: cannot find symbol
symbol : variable Invoer
location: class Euro
if(s.equals("Gulden > Euro") && Invoer.getText() != "")
^
C:\Program Files\Java\Java Development Kit\bin\Euro.java:73: operator * cannot be applied to double,java.lang.String
double d1 = double2.doubleValue() * koers.getText();
^
5 errors
Any ideas??