IN THIS POST I AM WRITING THE CODE FOR THE SIMPLE CALCULATOR BY USING THE APPLETS, AWT AND SWINGS

import javax.swing.*;

import java.awt.*;

import java.awt.event.*;

//<applet code=Calculator height=300 width=200></applet>

public class Calculator extends JApplet

{

public void init()

 {

CalculatorPanel calc=new CalculatorPanel();

getContentPane().add(calc);

}

}

class CalculatorPanel extends JPanel implements ActionListener

 {

JButton

n1,n2,n3,n4,n5,n6,n7,n8,n9,n0,plus,minus,mul,div,dot,equal;

static JTextField result=new JTextField("0",45);

static String lastCommand=null;

JOptionPane p=new JOptionPane();

double preRes=0,secVal=0,res;

private static void assign(String no)

{

if((result.getText()).equals("0"))

result.setText(no);

else if(lastCommand=="=")

{

result.setText(no);

lastCommand=null;

}

else

result.setText(result.getText()+no);

}

public CalculatorPanel()

{

setLayout(new BorderLayout());

result.setEditable(false);

result.setSize(300,200);

add(result,BorderLayout.NORTH);

JPanel panel=new JPanel();

panel.setLayout(new GridLayout(4,4));

n7=new JButton("7");

panel.add(n7);

n7.addActionListener(this);

n8=new JButton("8");

panel.add(n8);

n8.addActionListener(this);

n9=new JButton("9");

panel.add(n9);

n9.addActionListener(this);

div=new JButton("/");

panel.add(div);

div.addActionListener(this);

n4=new JButton("4");

panel.add(n4);

n4.addActionListener(this);

n5=new JButton("5");

panel.add(n5);

n5.addActionListener(this);

n6=new JButton("6");

panel.add(n6);

n6.addActionListener(this);

mul=new JButton("*");

panel.add(mul);

mul.addActionListener(this);

n1=new JButton("1");

panel.add(n1);

n1.addActionListener(this);

n2=new JButton("2");

panel.add(n2);

n2.addActionListener(this);

n3=new JButton("3");

panel.add(n3);

n3.addActionListener(this);

minus=new JButton("-");

panel.add(minus);

minus.addActionListener(this);

dot=new JButton(".");

panel.add(dot);

dot.addActionListener(this);

n0=new JButton("0");

panel.add(n0);

n0.addActionListener(this);

equal=new JButton("=");

panel.add(equal);

equal.addActionListener(this);

plus=new JButton("+");

panel.add(plus);

plus.addActionListener(this);

add(panel,BorderLayout.CENTER);

}

public void actionPerformed(ActionEvent ae)

{

if(ae.getSource()==n1) assign("1");

else if(ae.getSource()==n2) assign("2");

else if(ae.getSource()==n3) assign("3");

else if(ae.getSource()==n4) assign("4");

else if(ae.getSource()==n5) assign("5");

else if(ae.getSource()==n6) assign("6");

else if(ae.getSource()==n7) assign("7");

else if(ae.getSource()==n8) assign("8");

else if(ae.getSource()==n9) assign("9");

else if(ae.getSource()==n0) assign("0");

else if(ae.getSource()==dot)

{

if(((result.getText()).indexOf("."))==-1)

result.setText(result.getText()+".");

}

else if(ae.getSource()==minus)

{

preRes=Double.parseDouble(result.getText());

lastCommand="-";

result.setText("0");

}

else if(ae.getSource()==div)

{

preRes=Double.parseDouble(result.getText());

lastCommand="/";

result.setText("0");

}

else if(ae.getSource()==equal)

{

secVal=Double.parseDouble(result.getText());

if(lastCommand.equals("/"))

res=preRes/secVal;

else if(lastCommand.equals("*"))

res=preRes*secVal;

else if(lastCommand.equals("-"))

res=preRes-secVal;

else if(lastCommand.equals("+"))

res=preRes+secVal;

result.setText(" "+res);

lastCommand="=";

}

else if(ae.getSource()==mul)

{

preRes=Double.parseDouble(result.getText());

lastCommand="*";

result.setText("0");

}

else if(ae.getSource()==plus)

{

preRes=Double.parseDouble(result.getText());

lastCommand="+";

result.setText("0");

}

}     

 }

//execuation this is one way total html code and javacode in a single file

E:\jit>javac Calculator.java

E:\jit>appletviewer Calculator.java