My_Calculator.java

// program for calculator in java.

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

public class MyCalculator extends Frame
{
	public boolean setClear=true;
	double number, memValue;
	char op;
	String digitButtonText[] = {"7", "8", "9", "4", "5", "6", "1", "2", "3", "0", "+/-", "." };
	String operatorButtonText[] = {"/", "sqrt", "*", "%", "-", "1/X", "+", "=" };
	String memoryButtonText[] = {"MC", "MR", "MS", "M+" };
	String specialButtonText[] = {"Backspc", "C", "CE" };
	MyDigitButton digitButton[]=new MyDigitButton[digitButtonText.length];
	MyOperatorButton operatorButton[]=new MyOperatorButton[operatorButtonText.length];
	MyMemoryButton memoryButton[]=new MyMemoryButton[memoryButtonText.length];
	MySpecialButton specialButton[]=new MySpecialButton[specialButtonText.length];
	Label displayLabel=new Label("0",Label.RIGHT);
	Label memLabel=new Label(" ",Label.RIGHT);
	final int FRAME_WIDTH=325,FRAME_HEIGHT=325;
	final int HEIGHT=30, WIDTH=30, H_SPACE=10,V_SPACE=10;
	final int TOPX=30, TOPY=50;

	///////////////////////////
	MyCalculator(String frameText)//constructor
	{
		super(frameText);
		int tempX=TOPX, y=TOPY;
		displayLabel.setBounds(tempX,y,240,HEIGHT);
		displayLabel.setBackground(Color.BLUE);
		displayLabel.setForeground(Color.WHITE);
		add(displayLabel);
		memLabel.setBounds(TOPX, TOPY+HEIGHT+ V_SPACE,WIDTH, HEIGHT);
		add(memLabel);

		// set Co-ordinates for Memory Buttons
		tempX=TOPX;
		y=TOPY+2*(HEIGHT+V_SPACE);
		
		for(int i=0; i<memoryButton.length; i++)
		{
			memoryButton[i]=new MyMemoryButton(tempX,y,WIDTH,HEIGHT,memoryButtonText[i], this);
			memoryButton[i].setForeground(Color.WHITE);
			memoryButton[i].setBackground(Color.BLACK);
			y+=HEIGHT+V_SPACE;
		}

		//set Co-ordinates for Special Buttons
		tempX=TOPX+1*(WIDTH+H_SPACE); y=TOPY+1*(HEIGHT+V_SPACE);
		for(int i=0;i<specialButton.length;i++)
		{
			specialButton[i]=new MySpecialButton(tempX,y,WIDTH*2,HEIGHT,specialButtonText[i], this);
			specialButton[i].setForeground(Color.WHITE);
			specialButton[i].setBackground(Color.BLACK);
			tempX=tempX+2*WIDTH+H_SPACE;
		}
		
		//set Co-ordinates for Digit Buttons
		int digitX=TOPX+WIDTH+H_SPACE;
		int digitY=TOPY+2*(HEIGHT+V_SPACE);
		tempX=digitX; y=digitY;
		
		for(int i=0;i<digitButton.length;i++)
		{
			digitButton[i]=new MyDigitButton(tempX,y,WIDTH,HEIGHT,digitButtonText[i], this);
			digitButton[i].setForeground(Color.WHITE);
			digitButton[i].setBackground(Color.BLACK);
			tempX+=WIDTH+H_SPACE;
			if((i+1)%3==0){tempX=digitX; y+=HEIGHT+V_SPACE;}
		}

		//set Co-ordinates for Operator Buttons
		int opsX=digitX+2*(WIDTH+H_SPACE)+H_SPACE;
		int opsY=digitY;
		tempX=opsX; y=opsY;

		for(int i=0;i<operatorButton.length;i++)
		{
			tempX+=WIDTH+H_SPACE;
			operatorButton[i]=new MyOperatorButton(tempX,y,WIDTH,HEIGHT,operatorButtonText[i], this);
			operatorButton[i].setForeground(Color.WHITE);
			operatorButton[i].setBackground(Color.BLACK);
			
			if((i+1)%2==0){tempX=opsX; y+=HEIGHT+V_SPACE;}
		}
		
		addWindowListener(new WindowAdapter()
		{
			public void windowClosing(WindowEvent ev)
			{System.exit(0);}
		});

			setLayout(null);
			setSize(FRAME_WIDTH,FRAME_HEIGHT);
			setVisible(true);
	}

	static String getFormattedText(double temp)
	{
		String resText=""+temp;
		if(resText.lastIndexOf(".0")>0)
			resText=resText.substring(0,resText.length()-2);
		return resText;
	}
	
	public static void main(String []args)
	{
		new MyCalculator("Calculator");
	}
 }

	class MyDigitButton extends Button implements ActionListener
	{
		MyCalculator cl;
		MyDigitButton(int x,int y, int width,int height,String cap, MyCalculator clc)
		{
			super(cap);
			setBounds(x,y,width,height);
			this.cl=clc;
			this.cl.add(this);
			addActionListener(this);
		}

		static boolean isInString(String s, char ch)
		{
			for(int i=0; i<s.length();i++) if(s.charAt(i)==ch) return true;
			return false;
		}

		public void actionPerformed(ActionEvent ev)
		{
			String tempText=((MyDigitButton)ev.getSource()).getLabel();
			if(tempText.equals("."))
			{
				if(cl.setClear)
				{cl.displayLabel.setText("0.");cl.setClear=false;}
				else if(!isInString(cl.displayLabel.getText(),'.'))
					cl.displayLabel.setText(cl.displayLabel.getText()+".");
				return;
			}
			
			int index=0;
			try{
				index=Integer.parseInt(tempText);
			}catch(NumberFormatException e){return;}
			if (index==0 && cl.displayLabel.getText().equals("0")) return;
			if(cl.setClear)
			{cl.displayLabel.setText(""+index);cl.setClear=false;}
			else
				cl.displayLabel.setText(cl.displayLabel.getText()+index);
		}//actionPerformed
	}//class defination
	
	class MyOperatorButton extends Button implements ActionListener
	{
		MyCalculator cl;
		MyOperatorButton(int x,int y, int width,int height,String cap, MyCalculator clc)
		{
			super(cap);
			setBounds(x,y,width,height);
			this.cl=clc;
			this.cl.add(this);
			addActionListener(this);
		}
		
		public void actionPerformed(ActionEvent ev)
		{
			String opText=((MyOperatorButton)ev.getSource()).getLabel();
			cl.setClear=true;
			double temp=Double.parseDouble(cl.displayLabel.getText());
			if(opText.equals("1/x"))
			{
				try
				{double tempd=1/(double)temp;
				cl.displayLabel.setText(MyCalculator.getFormattedText(tempd));}
				catch(ArithmeticException excp)
				{cl.displayLabel.setText("Divide by 0.");}
				return;
			}
			if(opText.equals("sqrt"))
			{
				try
				{double tempd=Math.sqrt(temp);
				cl.displayLabel.setText(MyCalculator.getFormattedText(tempd));}
				catch(ArithmeticException excp)
				{cl.displayLabel.setText("Divide by 0.");}
				return;
			}
			if(!opText.equals("="))
			{
				cl.number=temp;
				cl.op=opText.charAt(0);
				return;
			}

			// process = button pressed
			switch(cl.op)
			{
				case '+':
					temp+=cl.number;break;
				case '-':
					temp=cl.number-temp;break;
				case '*':
					temp*=cl.number;break;
				case '%':
					try{temp=cl.number%temp;}
					catch(ArithmeticException excp)
					{cl.displayLabel.setText("Divide by 0."); return;}
					break;
				case '/':
					try{temp=cl.number/temp;}
					catch(ArithmeticException excp)
					{cl.displayLabel.setText("Divide by 0."); return;}
					break;
			}//switch

			cl.displayLabel.setText(MyCalculator.getFormattedText(temp));

			//cl.number=temp;
		}//actionPerformed
}//class
	
class MyMemoryButton extends Button implements ActionListener
{
	MyCalculator cl;
	MyMemoryButton(int x,int y, int width,int height,String cap, MyCalculator clc)
	{
		super(cap);
		setBounds(x,y,width,height);
		this.cl=clc;
		this.cl.add(this);
		addActionListener(this);
	}
	
	public void actionPerformed(ActionEvent ev)
	{
		char memop=((MyMemoryButton)ev.getSource()).getLabel().charAt(1);
		cl.setClear=true;
		double temp=Double.parseDouble(cl.displayLabel.getText());
		switch(memop)
		{
			case 'C':
				cl.memLabel.setText(" ");cl.memValue=0.0;break;
			case 'R':
				cl.displayLabel.setText(MyCalculator.getFormattedText(cl.memValue));break;
			case 'S':
				cl.memValue=0.0;
			case '+':
				cl.memValue+=Double.parseDouble(cl.displayLabel.getText());
				if(cl.displayLabel.getText().equals("0") || cl.displayLabel.getText().equals("0.0") )
					cl.memLabel.setText(" ");
				else
					cl.memLabel.setText("M");
				break;
		}//switch
	}//actionPerformed
}//class

class MySpecialButton extends Button implements ActionListener
{
	MyCalculator cl;
	MySpecialButton(int x,int y, int width,int height,String cap, MyCalculator clc)
	{
		super(cap);
		setBounds(x,y,width,height);
		this.cl=clc;
		this.cl.add(this);
		addActionListener(this);
	}

	static String backSpace(String s)
	{
		String Res="";
		for(int i=0; i<s.length()-1; i++) Res+=s.charAt(i);
		return Res;
	}

	public void actionPerformed(ActionEvent ev)
	{
		String opText=((MySpecialButton)ev.getSource()).getLabel();
		//check for backspace button
		if(opText.equals("Backspc"))
		{
			String tempText=backSpace(cl.displayLabel.getText());
			if(tempText.equals(""))
				cl.displayLabel.setText("0");
			else
				cl.displayLabel.setText(tempText);
			return;
		}
		
		//check for "C" button i.e. Reset
		if(opText.equals("C"))

		{
			cl.number=0.0; cl.op=' '; cl.memValue=0.0;
			cl.memLabel.setText(" ");
		}
		//it must be CE button pressed
		cl.displayLabel.setText("0");cl.setClear=true;
	}//actionPerformed
}