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

public class Calculator extends Applet implements ActionListener
{
	int currentValue = 0;
	int operand1     = 0;
	int operand2     = 0;
	int result;				// used to hold the calculated result
	int operation;       // 1 = add, 2 = subtract etc
	TextField calculatorDisplay = new TextField(" Hi There     ", 8);
	Panel numPanel = new Panel();
	Panel opsPanel = new Panel();
	Panel arrPanel = new Panel();
	Button butArray[] = new Button[10];
	Button one   = new Button("1");
	Button two   = new Button("2");
	Button three = new Button("3");
	Button four  = new Button("4");
	Button five  = new Button("5");
	Button six   = new Button("6");
	Button seven = new Button("7");
	Button eight = new Button("8");
	Button nine  = new Button("9");
	Button zero  = new Button("0");
	Button plus  = new Button("+");
	Button minus = new Button("-");
	Button times = new Button("*");
	Button divide = new Button("/");
	Button equals = new Button("=");
	Button clear  = new Button("clear");

	public void init()
	{
		numPanel.setLayout(new GridLayout(4,3,5,5));
		add(calculatorDisplay);
		numPanel.add(one);
		numPanel.add(two);
		numPanel.add(three);
		numPanel.add(four);
		numPanel.add(five);
		numPanel.add(six);
		numPanel.add(seven);
		numPanel.add(eight);
		numPanel.add(nine);
		numPanel.add(zero);
		
		opsPanel.setLayout(new GridLayout(2,4, 5, 5));		
		opsPanel.add(plus);
		opsPanel.add(minus);
		opsPanel.add(times);
		opsPanel.add(divide);
		opsPanel.add(equals);
		add(numPanel);
		add(opsPanel);
		add(clear);
		
		one.addActionListener(this);
		two.addActionListener(this);
		three.addActionListener(this);
		four.addActionListener(this);
		five.addActionListener(this);
		six.addActionListener(this);
		seven.addActionListener(this);
		eight.addActionListener(this);
		nine.addActionListener(this);
		zero.addActionListener(this);
		clear.addActionListener(this);
		plus.addActionListener(this);
		minus.addActionListener(this);
		times.addActionListener(this);
		divide.addActionListener(this);
		equals.addActionListener(this);
	
		arrPanel.setLayout(new GridLayout(4,3,5,5));
		for (int index = 0; index < 10; index++)
		{
			butArray[index] = new Button(Integer.toString(index));
			arrPanel.add(butArray[index]);
			butArray[index].addActionListener(this);
		}
		add(arrPanel);
		currentValue = 0;
	}
	
    public void actionPerformed(ActionEvent e)
   {
   		for (int index = 0; index < 10; index++)
		   {
		   	if (e.getSource() == butArray[index])
			   {
					currentValue = currentValue * 10 + index;
					calculatorDisplay.setText(Integer.toString(currentValue));
			   }
			}	
			if(e.getSource() == one)
			{
				currentValue = currentValue * 10 + 1;
				calculatorDisplay.setText(Integer.toString(currentValue));
			}
			else if(e.getSource() == two)
			{
				currentValue = currentValue * 10 + 2;
				calculatorDisplay.setText(Integer.toString(currentValue));
			}
			else if(e.getSource() == three)
			{
				currentValue = currentValue * 10 + 3;
				calculatorDisplay.setText(Integer.toString(currentValue));
			}
			else if(e.getSource() == four)
			{
				currentValue = currentValue * 10 + 4;
				calculatorDisplay.setText(Integer.toString(currentValue));
			}
			else if(e.getSource() == five)
			{
				currentValue = currentValue * 10 + 5;
				calculatorDisplay.setText(Integer.toString(currentValue));
			}
			else if(e.getSource() == six)
			{
				currentValue = currentValue * 10 + 6;
				calculatorDisplay.setText(Integer.toString(currentValue));
			}
			else if(e.getSource() == seven)
			{
				currentValue = currentValue * 10 + 7;
				calculatorDisplay.setText(Integer.toString(currentValue));
			}
			else if(e.getSource() == eight)
			{
				currentValue = currentValue * 10 + 8;
				calculatorDisplay.setText(Integer.toString(currentValue));
			}
			else if(e.getSource() == nine)
			{
				currentValue = currentValue * 10 + 9;
				calculatorDisplay.setText(Integer.toString(currentValue));
			}
			else if(e.getSource() == zero)
			{
				currentValue = currentValue * 10 + 0;
				calculatorDisplay.setText(Integer.toString(currentValue));
			}
			else if (e.getSource() == clear)
			{
				calculatorDisplay.setText("0");
				currentValue = 0;
				operand1     = 0;
				operand2     = 0;
			}
			else if (e.getSource() == plus)
			{
				operand1     = currentValue;
				currentValue = 0;
				calculatorDisplay.setText("0");
				operation    = 1;
			}
			else if (e.getSource() == minus)
			{
				operand1     = currentValue;
				currentValue = 0;
				calculatorDisplay.setText("0");
				operation    = 2;
			}				
			else if (e.getSource() == times)
			{
				operand1     = currentValue;
				currentValue = 0;
				calculatorDisplay.setText("0");
				operation    = 3;
			}				
			else if (e.getSource() == divide)
			{
				operand1     = currentValue;
				currentValue = 0;
				calculatorDisplay.setText("0");
				operation    = 4;
			}				
			else if (e.getSource() == equals)
			{
				operand2     = currentValue;
				currentValue = 0;
				switch (operation)
				{
					case 1: result = operand1  +  operand2; break;
					case 2: result = operand1  -  operand2; break;
					case 3: result = operand1  *  operand2; break;
					case 4: result = operand1  /  operand2; break;
				}
				calculatorDisplay.setText(Integer.toString(result));
				operand1 = operand2 = 0;
			
			}				
			
	}
		
	public void paint(Graphics g)
	{
		setForeground(Color.blue);
		setBackground(Color.yellow);
		g.drawString(" " + operand1 + "  " + operand2, 0, 380);
	}
}