Calculator on applet

Calculator In Java

import java.awt.*;
import java.awt.event.*;
import java.applet.*;

public class CalculatorApplet extends Applet implements ActionListener
{
private Button keysArray[];
private Panel keyPad;
private TextField lcdField;
private double result;
private boolean first;
private boolean foundKey;
static boolean clearText;
private int prevOperator;

public void init()
{
lcdField = new TextField(20);
keyPad = new Panel ();
keysArray = new Button[17];
result = 0.0;
prevOperator = 0;
first = true;
clearText = true;

//Set frame layout manager setLayout(new BorderLayout());

lcdField.setEditable(false);

//Create buttons
for (int i = 0; i <=9; i++)
keysArray[i] = new Button(String.valueOf(i));
keysArray[10] = new Button("/");
keysArray[11] = new Button("*");
keysArray[12] = new Button("-");
keysArray[13] = new Button("+");
keysArray[14] = new Button("=");
keysArray[15] = new Button(".");
keysArray[16] = new Button("CLR");

//Set panel layout manager
keyPad.setLayout(new GridLayout (4,4));

//Add button to keyPad panel
for (int i = 7; i <=10; i++) //adds Button 7,8,9, and divide to
Panel
keyPad.add(keysArray[i]);

for (int i = 4; i <6; i++) //adds buttons 4,5,6 to Panel
keyPad.add(keysArray[i]);

keyPad.add(keysArray[11]); //adds multiply button to Panel

for (int i = 1; i <= 3;i++) //adds buttons 1,2 and 3 to Panel
keyPad.add(keysArray[i]);

keyPad.add(keysArray[12]);//adds minus button to Panel

keyPad.add(keysArray[0]); //adds 0 key to Panel

for (int i = 15; i >=13; i--)
keyPad.add(keysArray[i]); //adds decimal point, equal, and addition
ke
ys Panel

add(lcdField, BorderLayout.NORTH); //adds text field to top of
Frame
add(keyPad, BorderLayout.CENTER); //adds Panel to center of Frame
add(keysArray[16], BorderLayout.EAST); //adds Clear key to right
side
of applet

for(int i = 0; i < keysArray.length; i++)
keysArray[i].addActionListener(this);
}

public void actionPerformed(ActionEvent e)
{
foundKey = false;

//Search for the key pressed
for (int i = 0; i < keysArray.length && !foundKey; i++)
if(e.getSource() == keysArray[i]) //key match found
{
foundKey = true;
switch(i)
{
case 0: case 1: case 2: case 3: case 4: //number buttons
case 5: case 6: case 7: case 8: case 9: //0-9
case 15:
if (clearText)
{
lcdField.setText("");
clearText = false;
}
lcdField.setText(lcdField.getText() +
keysArray[i].getLabel());
break;

case 10:// divide button
case 11:// multiply button
case 12:// minus button
case 13:// plus button
case 14:// equal button
clearText = true;
if (first) // First operand
{
if(lcdField.getText().length()==0)
result = 0.0;
else
result = Double.valueOf(lcdField.getText()).doubleValue();

first = false;
prevOperator = i; //save previous operator
}
else //second operand already enter, so calculator total
{
switch(prevOperator)
{
case 10: //divide Button
result /= Double.valueOf(lcdField.getText()).
doubleValue();
break;
case 11: //multiply Button
result *= Double.valueOf(lcdField.getText()).
doubleValue();
break;
case 12: //minus button
result -= Double.valueOf(lcdField.getText()).
doubleValue();
break;
case 13: //plus button
result += Double.valueOf(lcdField.getText()).
doubleValue();
break;
}
lcdField.setText(Double.toString(result));
if (i==14)//equal button
first = true;
else
prevOperator = i; //save previous opetator
}
break;

case 16://Clear button
clearText = true;
first = true;
lcdField.setText("");
result = 0.0;
prevOperator = 0;
break;
}
}
}
}