Advice wanted: do i need threads or not?Stuck!

Question

Hi, everyone! I got stuck with little program I'm writing and need your advice desperately.
I am doing temperature conversion program. In short, it's an applet with two JTextFields and four panels. JTextFields belong to the applet. Two panels are derivatives from my class called BasicThermometer extends JPanel. I made this class as flexible as I could, and it can draw pretty thermometer with needed ticks and ticks' labels as needed.
So, I've put two BasicTherm-s into my applet representing Celsius and Fahrenheit therm-rs respectively.
Other two panels are derivatives from my GradientPanel extends JPanel. They have gradient painted background with red and blue colors.
OK, here my final goal. When user input temp. to be converted in either text field converted temp. appears in other text field and tungsten of each therm-r reacts accordingly (I did that).
I can not accomplish my other task. Tungsten of each therm. responds on mouse event, so the user can input temp. by dragging or clicking it on either therm-r.( It's reacting allright). I want the temperature appear in each textfield and other therm-r tungsten move accordingly. I am unable to determine wether I need threads in it and if I do, how to design them. Should it be one thread or two? I am very new to multithreading and everything there is still blur to me. Also I'd like my gradient panels to react by fading gradient or thicken it on red (upper) panel or blue(lower panel).
I already set it flexible, so it's not a problem if I only could coordinate all my events properly.
Any advice will be helpful for me. I mean, maybe I have to change something in my classes-subclasses. To create new constructors maybe? How to deliver events from one JPanel so that the applet knew and pass it to other JPanel (i.e. to other BasicThermometer) so to repaint it as I want.In my thinking there could be thread or two that constatly tested one or other therm-r (while GUI thread is idling) and pass results to applet's method which resets other therm-r. Yesterday I failed to make them work. They worked two rounds right after start() even though my permit was set to false in each of the thermometers, and then stopped and did not wake if I clicked on either therm (I tested them by passing messages to be displayed in DOS).
Well, I am very confused. Sorry for lengthy message.
Svetlana

Answer 1

try my code
import java.awt.*;
import java.applet.Applet;
import java.awt.event.*;
<applet code="CtoFConversion1.class" width=170 height = 170>
</applet>
public class CtoFConversion1 extends Applet implements ActionListener, ItemListener {
float c=0.0f;
float f=0.0f;
String msg="";
Checkbox checkbox1, checkbox2;
CheckboxGroup cbg;
TextField tf1,tf2;
Button convert, reset;
public void init() {
cbg = new CheckboxGroup();
checkbox1 = new Checkbox("Convert C to F",cbg, true);
checkbox2 = new Checkbox("Convert F to C",cbg, false);
convert = new Button("Convert");
reset = new Button("Reset");
Label centigrade = new Label("Centigrade :", Label.RIGHT);
Label fahrenheit = new Label("Fahrenheit :", Label.RIGHT);
tf1 = new TextField(10);
tf2 = new TextField(10);
add(checkbox1);
add(checkbox2);
add(centigrade);
add(tf1);
add(fahrenheit);
add(tf2);
add(convert);
add(reset);
checkbox1.addItemListener(this);
checkbox2.addItemListener(this);
tf1.addActionListener(this);
tf2.addActionListener(this);
convert.addActionListener(this);
reset.addActionListener(this);
tf2.setEditable(false);
public void itemStateChanged(ItemEvent ie) {
if((cbg.getSelectedCheckbox().getLabel()).equals("Convert C to F")) {
tf2.setEditable(false);
tf1.setEditable(true);
repaint();
if((cbg.getSelectedCheckbox().getLabel()).equals("Convert F to C")) {
tf1.setEditable(false);
tf2.setEditable(true);
repaint();
public void actionPerformed(ActionEvent ae) {
String command = ae.getActionCommand();
if(command.equals("Convert")) {
if((cbg.getSelectedCheckbox().getLabel()).equals("Convert C to F")) {
tf2.setEditable(false);
tf1.setEditable(true);
msg = tf1.getText();
try {
c = new Float(msg).floatValue();
msg="";
centi(c);
msg = msg+f;
tf2.setText(msg);
repaint();
}catch(NumberFormatException e){
tf2.setText("Syntax Error");
else if((cbg.getSelectedCheckbox().getLabel()).equals("Convert F to C")) {
tf1.setEditable(false);
tf2.setEditable(true);
msg = tf2.getText();
try {
c = new Float(msg).floatValue();
msg="";
fahren(c);
msg = msg+f;
tf1.setText(msg);
repaint();
}catch(NumberFormatException e){
tf1.setText("Syntax Error");
else if (command.equals("Reset")) {
tf2.setEditable(false);
tf1.setText("");
tf1.setEditable(true);
tf2.setText("");
checkbox1.setState(true);
repaint();
public float centi(float c){
f = (float)(1.8*c)+32.0f;
return f;
public float fahren(float c){
f = (float)(0.5556*(c-32.0));
return f;
}