Why it is error? (Function)

Question

Hello,
I am trying to write a program to calculate a function like f(x) = asin(x+b)exp(cx) where a,b,c, and x is unfixed and users can input their values. After input all values of a,b,c and x, users click a button named "result", and result of that function is appeared. values of a,b,c, and x can be decimal point and negative. Below is my program. However, when I compile, it said that error at the line of " public void init(){". Can anyone help me to solve this problem please!
//Main method
import java.awt.*;
import java.awt.event.*;
import java.applet.*;
import java.lang.Math;
public class Function extends Applet implements
ActionListener
TextField textField1;
TextField textField2;
TextField textField3;
TextField textField4;
public void init()
textField1 = new TextField(5);
textField2 = new TextField(5);
textField3 = new TextField(5);
textField4 = new TextField(5);
add (textField1);
add (textField2);
add (textField3);
add (textField4);
textField1.setText("0");
textField2.setText("0");
textField3.setText("0");
textField4.setText("0");
textField1.addActionListener (this);
textField2.addActionListener (this);
textField3.addActionListener (this);
textField4.addActionListener (this);
public void paint (Graphics g) {
double value1;
double value2;
double value3;
double value4;
     double function;
String s = textField1.getText ();
value1 = Integer.parseInt (s);
s = textField2.getText ();
value2 = Integer.parseInt (s);
s = textField3.getText ();
value3 = Integer.parseInt (s);
s = textField4.getText ();
value4 = Integer.parseInt (s);
double function = value1 * Math.sin ( value4 + value2 ) * Math.exp ( value3 * value4 );
s = String.valueOf(function);
g.drawString (s, 140, 200);
public void actionPerformed (ActionEvent event) {
repaint ();
// this is another file for execute the frame
public class Application {
/* Constructor */
public Application() {
Function frame = new Function();
frame.setVisible(true);
/* Main method */
public static void main(String[] args) {
new Application();

Answer 1

Sorry,
I made a mistake this morning to upload the wrong program. Following is the one I want to ask for help. I am using J2SDK1.4.1 beta. However, the error message is in Japanese which I could not understand, because I am using Japanese Windown version, and I do not know how to install Java development kit in English.
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.lang.Math;
public class Frame extends JFrame {
     JPanel contentPane;
     JLabel L1 = new JLabel();
     JLabel L2 = new JLabel();
     JLabel L3 = new JLabel();
     JLabel L4 = new JLabel();
     JLabel L5 = new JLabel();
     JLabel L6 = new JLabel();
     JLabel L7 = new JLabel();
     JButton jButton1 = new JButton();
     JButton jButton2 = new JButton();
     JButton jButton3 = new JButton();
     JButton jButton4 = new JButton();
     JButton jButton5 = new JButton();
/*Construction of a frame*/
public Frame() {
/* Text Label */
L1.setText("f(x) = ");
L1.setBounds(14, 39, 163, 35);
L2.setText("sin (x + ");
L2.setBounds(140, 39, 163, 35);
L3.setText(") exp (");
L3.setBounds(240, 39, 163, 35);
L4.setText("x )");
L4.setBounds(340, 39, 163, 35);
L5.setText("f ( ");
L5.setBounds(14, 89, 163, 35);
L6.setText(" ) =");
L6.setBounds(140, 89, 163, 35);
L7.setText(" ? ? ?");
L7.setBounds(140, 109, 163, 35);
     contentPane = (JPanel) this.getContentPane();
     contentPane.setLayout(null);
this.setSize(650,350);
/* Set textfield for user to add value */
public void init {
     TextField textField1;
     TextField textField2;
     TextField textField3;
     TextField textField4;
     textField1 = new JTextField(5);
     textField2 = new JTextField(5);
     textField3 = new JTextField(5);
     textField4 = new JTextField(5);
     add (textField1);
     add (textField2);
     add (textField3);
     add (textField4);
     textField1.setText("0");
     textField2.setText("0");
     textField3.setText("0");
     textField4.setText("0");
textField1.addActionListener (this);
textField2.addActionListener (this);
textField3.addActionListener (this);
textField4.addActionListener (this);
public void paint (Graphics g)
double value1;
double value2;
double value3;
double value4;
double function;
String s = textField1.getText ();
value1 = Integer.parseInt (s);
s = textField2.getText ();
value2 = Integer.parseInt (s);
s = textField3.getText ();
value3 = Integer.parseInt (s);
s = textField4.getText ();
value4 = Integer.parseInt (s);
double function = value1 * Math.sin ( value4 + value2 ) * Math.exp ( value3 * value4 );
s = String.valueOf(function);
s.setBounds(240, 89, 163, 35);
public void actionPerformed (ActionEvent e) {
repaint ();
return true;
/* Setting a button */
jButton1.setText("Result");
jButton1.setBounds(240, 89, 96, 41);
jButton1.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent e) {
L7.setText("+ function");
contentPane.add(jButton1, null);
contentPane.add(L1, null);
contentPane.add(L2, null);
contentPane.add(L3, null);
contentPane.add(L4, null);
contentPane.add(L5, null);
contentPane.add(L6, null);
contentPane.add(L7, null);