It compiles but can't run it!

Question

Hi
I am really new to java. I got this code from net and tried to compile it. Idoes compile but when i run it , i get the messege,
"java.lang.NoSuchMethodError: main
Exception in thread "main" .
Here is me code.Can someone pleaese tell me y i can't run it and how to fix it. Thanks for your time.
import java.awt.*;
import java.awt.event.*;
public class calculator extends java.applet.Applet implements ActionListener {
     TextField txtTotal = new TextField("");
Button button[] = new Button[10];
     Button divide = new Button("/");
     Button mult = new Button("*");
     Button plus = new Button ("+");
     Button minus = new Button("-");
     Button isequalto = new Button("=");
     Button clear = new Button("CA");
     double num ,numtemp ;
     int counter;
     String strnum = "",strnumtemp = "" ;
     String op = "";
     public void operation() {
     counter ++;
          if (counter == 1) {
          numtemp = num;      
          strnum = "";
          num = 0;
          }else{
          if (op == "+") numtemp += num;
          else if (op == "-") numtemp -= num;
          else if (op == "*") numtemp = numtemp * num;
          else if (op == "/") numtemp = numtemp / num;
          strnumtemp = Double.toString(numtemp);
          txtTotal.setText(strnumtemp);          
          strnum = "";
          num = 0;     
     public void init() {
     setLayout(null);
     plus.setBackground(Color.blue);
     plus.setForeground(Color.white);
minus.setBackground(Color.blue);
     minus.setForeground(Color.white);
divide.setBackground(Color.blue);
     divide.setForeground(Color.white);
     isequalto.setBackground(Color.blue);
     isequalto.setForeground(Color.white);
     mult.setBackground(Color.blue);
     mult.setForeground(Color.white);
     clear.setBackground(Color.blue);
     clear.setForeground(Color.red);
     for(int i = 0;i <= 9; i ++) {
          button[i] = new Button(String.valueOf(i));
          button.setBackground(Color.orange);
          button[i].setForeground(Color.blue);
     button[1].setBounds(0,53,67,53);
     button[2].setBounds(67,53,67,53);
     button[3].setBounds(134,53,67,53);
     button[4].setBounds(0,106,67,53);
     button[5].setBounds(67,106,67,53);
     button[6].setBounds(134,106,67,53);
     button[7].setBounds(0,159,67,53);
     button[8].setBounds(67,159,67,53);
     button[9].setBounds(134,159,67,53);
     for (int i = 1;i <= 9; i ++) {
          add(button[i]);
     txtTotal.setBounds(0,0,200,53);
     add(txtTotal);
     plus.setBounds(0,212,67,53);
     add(plus);
     button[0].setBounds(67,212,67,53);
     add(button[0]);
     minus.setBounds(134,212,67,53);
     add(minus);
     divide.setBounds(134,264,67,53);
     add(divide);
     isequalto.setBounds(67,264,67,53);
     add(isequalto);
     mult.setBounds(0,264,67,53);
     add(mult);
     add(clear);
     public void start() {
     for(int i = 0;i <= 9; i ++) {
          button[i].addActionListener(this);
     plus.addActionListener(this);
     minus.addActionListener(this);
     divide.addActionListener(this);
     mult.addActionListener(this);
     isequalto.addActionListener(this);
     clear.addActionListener(this);
     public void stop() {
     for(int i = 0;i <= 9; i ++) {
          button[i].addActionListener(null);
     plus.addActionListener(null);
     minus.addActionListener(null);
     divide.addActionListener(null);
     mult.addActionListener(null);
     isequalto.addActionListener(null);
     clear.addActionListener(null);
     public void actionPerformed(ActionEvent e) {
          for(int i = 0;i <= 9; i++) {
               if (e.getSource() == button[i]) {
               play(getCodeBase(),i + ".au");
               strnum += Integer.toString(i);
               txtTotal.setText(strnum);
               num = Double.valueOf(strnum).doubleValue();
if (e.getSource() == plus) {
          operation();
          op = "+";
          if (e.getSource() == minus) {
          operation();
          op = "-";
          if (e.getSource() == divide) {
          operation();     
          op = "/";
          if (e.getSource() == mult) {
          operation();     
          op = "*";
          if (e.getSource() == isequalto) {
          if (op == "+") numtemp += num;
          else if (op == "-") numtemp -= num;
          else if (op == "*") numtemp = numtemp * num;
          else if (op == "/") numtemp = numtemp / num;
          strnumtemp = Double.toString(numtemp);
          txtTotal.setText(strnumtemp);
          strnumtemp = "";
          numtemp = 0;
          strnum = "";
          num = 0;
          counter = 0;
          if (e.getSource() == clear) {
          txtTotal.setText("0");
          strnumtemp = "";
          numtemp = 0;
          strnum = "";
          num = 0;
          counter = 0;

Answer 1

Thanks for your reply.
Ok i used the link that you sent me and saved the following in the same directory where i have "calcultor.class".
<HTML>
<HEAD>
<TITLE> A Simple Program </TITLE>
</HEAD>
<BODY>
<APPLET CODE="calculator.class" WIDTH=150 HEIGHT=25>
</APPLET>
</BODY>
</HTML>
I saved it with the name "calculator.html".
Now when in my browser i type calculator.html, nothing happens.
I am sure i am missing something but i don't know what.Can someone please help me!
thanks