A Simple Calculator in Java

Hi Friends....just had some free time, so thought of creating a "Simple Calculator" in Java...As claims it is "Simple" and don't expect anything Big out of it (Just some basic operations).....I have added the source code for it too....

(You can use it to Create your own Calculator and may be which is more efficient than mine..Just in case u find any flaws in this, pls do mail me abt it..)

Screenshot of "Calculator" that I created in Java



Download the "Calculator"

Download the Source Code

Code of Calculator.java

// Initial Declarations

import javax.swing.*;
import javax.swing.event.*;
import java.awt.*;
import java.awt.event.*;

// Creating a class named Calculator

class Calculator
{

// Components that are required to create the Calculator

JFrame frame = new JFrame();
// Creating the Menu Bar
JMenuBar menubar = new JMenuBar();
//---> Creating the "Calculator-->Exit" Menu
JMenu firstmenu = new JMenu("Calculator");
JMenuItem exitmenu = new JMenuItem("Exit");
// Creating The TextArea that gets the value
JTextField editor = new JTextField();
JRadioButton degree = new JRadioButton("Degree");
JRadioButton radians = new JRadioButton("Radians");

String[] buttons = {"BKSP","CLR","sin","cos","tan","7","8","9","/","+/-","4","5","6","X","x^2","1","2","3","-","1/x","0",".","=","+","sqrt"};

JButton[] jbuttons = new JButton[26];
double buf=0,result;
boolean opclicked=false,firsttime=true;
String last_op;

// Creating a Constructor to Initialize the Calculator Window

public Calculator()
{
frame.setSize(372,270);
frame.setTitle("Calculator - By G.Vivek Venkatesh.");
frame.setLayout(new BorderLayout());
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setResizable(false);

ButtonHandler bhandler = new ButtonHandler();

menubar.add(firstmenu);
firstmenu.add(exitmenu);
exitmenu.setActionCommand("mExit");
exitmenu.addActionListener(bhandler);

editor.setPreferredSize(new Dimension(20,50));

Container buttoncontainer = new Container();

buttoncontainer.setLayout(new GridLayout(5,5));
for(int i=0;i {
jbuttons[i] = new JButton(buttons[i]);
jbuttons[i].setActionCommand(buttons[i]);
jbuttons[i].addActionListener(bhandler);
buttoncontainer.add(jbuttons[i]);
}
JPanel degrad = new JPanel();
degrad.setLayout(new FlowLayout());
ButtonGroup bg1 = new ButtonGroup();
bg1.add(degree);
bg1.add(radians);
degrad.add(degree);
radians.setSelected(true);
degrad.add(radians);

frame.setJMenuBar(menubar);
frame.add(editor,BorderLayout.NORTH);
frame.add(degrad,BorderLayout.CENTER);
frame.add(buttoncontainer,BorderLayout.SOUTH);
frame.setVisible(true);
}

// Class that handles the Events (that implements ActionListener)

public class ButtonHandler implements ActionListener
{
public void actionPerformed(ActionEvent e)
{
String action = e.getActionCommand();
if(action == "0" || action=="1" || action=="2" || action=="3" || action=="4" || action=="5" || action=="6" || action=="7" || action=="8" || action=="9" || action==".")
{
if(opclicked == false)
editor.setText(editor.getText() + action);
else
{
editor.setText(action);
opclicked = false;
}
}
if(action == "CLR")
{
editor.setText("");
buf=0;
result=0;
opclicked=false;
firsttime=true;
last_op=null;
}
//Addition
if(action=="+")
{
firsttime = false;
if(last_op!="=" && last_op!="sqrt" && last_op!="1/x" && last_op!="x^2" && last_op!="+/-")
{
buf = buf + Double.parseDouble(editor.getText());
editor.setText(Double.toString(buf));
last_op = "+";
opclicked=true;
}
else
{
opclicked=true;
last_op = "+";
}
}
// Subtraction
if(action=="-")
{
if(firsttime==true)
{
buf = Double.parseDouble(editor.getText());
firsttime = false;
opclicked=true;
last_op = "-";
}
else
{
if(last_op!="=" && last_op!="sqrt" && last_op!="1/x" && last_op!="x^2" && last_op!="+/-")
{
buf = buf - Double.parseDouble(editor.getText());
editor.setText(Double.toString(buf));
last_op = "-";
opclicked=true;
}
else
{
opclicked=true;
last_op = "-";
}
}
}
//Multiplication
if(action=="X")
{
if(firsttime==true)
{
buf = Double.parseDouble(editor.getText());
firsttime = false;
opclicked = true;
last_op = "X";
}
else
{
if(last_op!="=" && last_op!="sqrt" && last_op!="1/x" && last_op!="x^2" && last_op!="+/-")
{
buf = buf * Double.parseDouble(editor.getText());
editor.setText(Double.toString(buf));
last_op = "X";
opclicked=true;
}
else
{
opclicked=true;
last_op = "X";
}
}
}
//Division
if(action=="/")
{
if(firsttime==true)
{
buf = Double.parseDouble(editor.getText());
firsttime = false;
opclicked=true;
last_op = "/";
}
else
{
if(last_op!="=" && last_op!="sqrt" && last_op!="1/x" && last_op!="x^2" && last_op!="+/-")
{
buf = buf / Double.parseDouble(editor.getText());
editor.setText(Double.toString(buf));
last_op = "/";
opclicked=true;
}
else
{
opclicked=true;
last_op = "/";
}
}
}
// Equal to
if(action=="=")
{
result = buf;
if(last_op=="+")
{
result = buf + Double.parseDouble(editor.getText());
buf = result;
}
if(last_op=="-")
{
result = buf - Double.parseDouble(editor.getText());
buf = result;
}
if(last_op=="X")
{
result = buf * Double.parseDouble(editor.getText());
buf = result;
}
if(last_op=="/")
{
try
{
result = buf / Double.parseDouble(editor.getText());
}
catch(Exception ex)
{
editor.setText("Math Error " + ex.toString());

}
buf = result;
}

editor.setText(Double.toString(result));
last_op = "=";
}
// Sqrt
if(action=="sqrt")
{

if(firsttime==false)
{
buf = Math.sqrt(buf);
editor.setText(Double.toString(buf));
opclicked=true;
last_op = "sqrt";
}
else
{
if(editor.getText()=="")
JOptionPane.showMessageDialog(frame,"Enter input pls...","Input Missing",JOptionPane.ERROR_MESSAGE);
else
{
buf = Double.parseDouble(editor.getText());
buf = Math.sqrt(buf);
editor.setText(Double.toString(buf));
firsttime = false;
opclicked=true;
last_op = "sqrt";
}
}

}
// Reciprocal

if(action=="1/x")
{

if(firsttime==false)
{
buf = 1/ buf;
editor.setText(Double.toString(buf));
opclicked=true;
last_op = "1/x";
}
else
{
if(editor.getText()==null)
JOptionPane.showMessageDialog(frame,"Enter input pls...","Input Missing",JOptionPane.ERROR_MESSAGE);
else
{
buf = Double.parseDouble(editor.getText());
buf = 1 / buf;
editor.setText(Double.toString(buf));
firsttime = false;
opclicked=true;
last_op = "1/x";
}
}

}

// Square

if(action=="x^2")
{

if(firsttime==false)
{
buf = buf * buf;
editor.setText(Double.toString(buf));
opclicked=true;
last_op = "x^2";
}
else
{
if(editor.getText()==null)
JOptionPane.showMessageDialog(frame,"Enter input pls...","Input Missing",JOptionPane.ERROR_MESSAGE);
else
{
buf = Double.parseDouble(editor.getText());
buf = buf * buf;
editor.setText(Double.toString(buf));
firsttime = false;
opclicked=true;
last_op = "x^2";
}
}

}

// Negation +/-
if(action=="+/-")
{

if(firsttime==false)
{
buf = -(buf);
editor.setText(Double.toString(buf));
opclicked=true;
last_op = "+/-";
}
else
{
if(editor.getText()==null)
JOptionPane.showMessageDialog(frame,"Enter input pls...","Input Missing",JOptionPane.ERROR_MESSAGE);
else
{
buf = Double.parseDouble(editor.getText());
buf = -(buf);
editor.setText(Double.toString(buf));
firsttime = false;
opclicked=true;
last_op = "+/-";
}
}

}
// Exit
if(action=="mExit")
{
frame.dispose();
System.exit(0);
}
if(action=="mCut")
editor.cut();
if(action=="mCopy")
editor.copy();
if(action=="mPaste")
editor.paste();
if(action=="sin")
{
if(radians.isSelected())
{
if(firsttime==false)
{
buf = Math.sin(Double.parseDouble(editor.getText()));
editor.setText(Double.toString(buf));
opclicked=true;
last_op = "sin";
}
else
{
if(editor.getText()=="")
JOptionPane.showMessageDialog(frame,"Enter input pls...","Input Missing",JOptionPane.ERROR_MESSAGE);
else
{
buf = Double.parseDouble(editor.getText());
buf = Math.sin(Double.parseDouble(editor.getText()));
editor.setText(Double.toString(buf));
firsttime = false;
opclicked=true;
last_op = "sin";
}
}
}
else
{
if(firsttime==false)
{
double rad=Math.toRadians(Double.parseDouble(editor.getText()));
buf = Math.sin(rad);
editor.setText(Double.toString(buf));
opclicked=true;
last_op = "sin";
}
else
{
if(editor.getText()=="")
JOptionPane.showMessageDialog(frame,"Enter input pls...","Input Missing",JOptionPane.ERROR_MESSAGE);
else
{
double rad=Math.toRadians(Double.parseDouble(editor.getText()));
buf = Math.sin(rad);
editor.setText(Double.toString(buf));
firsttime = false;
opclicked=true;
last_op = "sin";
}
}
}
}// end of sin

if(action=="cos")
{
if(radians.isSelected())
{
if(firsttime==false)
{
buf = Math.cos(Double.parseDouble(editor.getText()));
editor.setText(Double.toString(buf));
opclicked=true;
last_op = "cos";
}
else
{
if(editor.getText()=="")
JOptionPane.showMessageDialog(frame,"Enter input pls...","Input Missing",JOptionPane.ERROR_MESSAGE);
else
{
buf = Double.parseDouble(editor.getText());
buf = Math.sin(Double.parseDouble(editor.getText()));
editor.setText(Double.toString(buf));
firsttime = false;
opclicked=true;
last_op = "cos";
}
}
}
else
{
if(firsttime==false)
{
double rad=Math.toRadians(Double.parseDouble(editor.getText()));
buf = Math.cos(rad);
editor.setText(Double.toString(buf));
opclicked=true;
last_op = "cos";
}
else
{
if(editor.getText()=="")
JOptionPane.showMessageDialog(frame,"Enter input pls...","Input Missing",JOptionPane.ERROR_MESSAGE);
else
{
double rad=Math.toRadians(Double.parseDouble(editor.getText()));
buf = Math.cos(rad);
editor.setText(Double.toString(buf));
firsttime = false;
opclicked=true;
last_op = "cos";
}
}
}
}// end of cos
if(action=="tan")
{
if(radians.isSelected())
{
if(firsttime==false)
{
buf = Math.tan(Double.parseDouble(editor.getText()));
editor.setText(Double.toString(buf));
opclicked=true;
last_op = "tan";
}
else
{
if(editor.getText()=="")
JOptionPane.showMessageDialog(frame,"Enter input pls...","Input Missing",JOptionPane.ERROR_MESSAGE);
else
{
buf = Double.parseDouble(editor.getText());
buf = Math.tan(Double.parseDouble(editor.getText()));
editor.setText(Double.toString(buf));
firsttime = false;
opclicked=true;
last_op = "tan";
}
}
}
else
{
if(firsttime==false)
{
double rad=Math.toRadians(Double.parseDouble(editor.getText()));
buf = Math.tan(rad);
editor.setText(Double.toString(buf));
opclicked=true;
last_op = "tan";
}
else
{
if(editor.getText()=="")
JOptionPane.showMessageDialog(frame,"Enter input pls...","Input Missing",JOptionPane.ERROR_MESSAGE);
else
{
double rad=Math.toRadians(Double.parseDouble(editor.getText()));
buf = Math.tan(rad);
editor.setText(Double.toString(buf));
firsttime = false;
opclicked=true;
last_op = "tan";
}
}
}
}// end of tan
}
}
}


Comments are welcomed....(Although care has been taken it may contain logical errors or bugs, because I did it in few hours....)