GUI Calculator

Question

Hello everyone! I'm trying to create a GUI Calculator but cannot get my program to compile. Please could someone assist me, thanks.
import java.io.*;
import java.util.*;
import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
public class CalculatorFrame extends JFrame
private Container contentPane;
//The componenets used in the calculator
private JTextField display;
private JButton addition;
private JButton subtract;
private JButton multiply;
private JButton divide;
private JButton mod;
private JButton enter;
private JButton [] digits;
//End of components
//Integer representations for the arithmetic operations needed
private final static int ADD = 1;
private final static int SUB = 2;
private final static int MUL = 3;
private final static int DIV = 4;
private final static int MOD = 5;
//ENd of arithmethic operations
//Integer holding the operator that the user requested
private int op;
//Boolean variable to help perform the calculations
private boolean firstFilled;
private boolean clearScreen;
//Constructor for the class
public CalculatorFrame()
contentPane=new Container();
this.setSize(400,300); //sets the size of the frame
this.setTitle("MIS 222 Calculator"); //sets the title of the frame
//allows the "X" box in the upper right hand corner to close the entire application
this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
contentPane=this.getContentPane(); //gets the content pane
//Methods
addDisplay();
addDigits();
addDigitActionListeners();
addOperation();
private void addDisplay()
JLabel displayLab = new JLabel("Answer");
JPanel north = new JPanel();
north.add(displayLab);
contentPane.add(north, "North");
//diplay was already declared above the constructor
display = new JTextField(25);
//adding the components to the panel
north.add(displayLab);
north.add(display);
//adding the panel to frame's content pane
contentPane.add(north, "North");
//Declaring the global digits array
private void addDigits()
//Add 1 large panel to hold the 3 inner panels
JPanel digPanel = new JPanel();
//Set the panel's preferred size so that it will keep everything in line
digPanel.setPreferredSize(new Dimension(200, 275));
//Initialize the top 3 digits' JPanel and set its preferrd size
JPanel topDigits = new JPanel();
topDigits.setPreferredSize(new Dimension(200,60));
//Initialize the middle 2 digits' JPanel and set its preferred size
JPanel midDigits = new JPanel();
midDigits.setPreferredSize(new Dimension(200,60));
//Initialize the bottom digits' JPanel and set its preferred size
JPanel botDigits = new JPanel();
botDigits.setPreferredSize(new Dimension(200, 75));
//Initialize the JButton array
digits = new JButton[11];
//Initialize each of the top Panel's digit buttons, and add it to the top panel
for(int i=1; i<4; i++)
String lab=(new Integer(i)).toString();
digits=new JButton(lab);
topDigits.add(digits);
//Adding the top Digit Panel to the overall digit panel
digPanel.add(topDigits, BorderLayout.CENTER);
//Adding the middle Digit Panel to the overall digit panel
digPanel.add(midDigits, BorderLayout.CENTER);
//Adding the bottom Digit Panel to the overall digit panel
digPanel.add(botDigits, BorderLayout.CENTER);
//Add the overall digit Panel to the Frame's contentpane
contentPane.add(digPanel, BorderLayout.CENTER);
//Method created to add the DigitAction Listeners
addDigitActionListeners();
//Method created to add all of the DigitActionListeners
private void addDigitActionListeners()
for(int i=0; i<10; i++)
digits.addActionListener(new DigitActionListener(i));
digits[10].addActionListener(new DigitActionListener("."));
//DigitActionListener class
public class DigitActionListener implements ActionListener
private String myNum;
public DigitActionListener(int num)
myNum=""+num;
public DigitActionListener(String num)
myNum=num;
public void actionPerformed(ActionEvent e)
if(display.getText().equals("Please enter a valid number")|| clearScreen)
clearScreen=false;
display.setText("");
//OperatorActionListener class
public void OpActionListener implements ActionListener
private int myOpNum;
public OpActionListener(int op)
myOpNum=op;
public void actionPerformed(ActionEvent e)
{ //Checks to see if the user has already enterd a number
if(!firstFilled)
try{
//Parse the number entered
String number=display.getText();
dNum1=Double.parseDouble(number);
//Sets the flag for the firstFilled to true
firstFilled=true
//Sets the op variable so when the "Enter" button is pressed, it will know which operation to perform
op=myOpNum;
//Clears the textbox
display.setText("");
catch(Exception er)
display.setText("Please enter a valid number");
//This is the second number being entered
else{
try{
String number=display.getText();
String result;
dNum2=Double.parseDouble(number);
firstFilled=true;
op=myOpNum;
display.setText("");
catch(Exception er)
display.setText("Please enter a valid number");
private void addOperation()
JPanel opPanel=new JPanel();
opPanel.setPreferredSize(new Dimension(75,200));
JButton clear = new JButton("C");
JButton addition = new JButton("+");
JButton subtraction = new JButton("-");
JButton multiply = new JButton("*");
JButton divide = new JButton("/");
JButton mod = new JButton("%");
JButton enter = new JButton("Enter");
addition.addActionListener(new OpActionListener(ADD));
subtraction.addActionListener(new OpActionListener(SUB));
multiply.addActionListener(new OpActionListener(MUL));
divide.addActionListener(new OpActionListener(DIV));
mod.addActionListener(new OpActionListener(MOD));
clear.addActionListener(new ActionListener()
public void actionPerformed(ActionEvent e)
display.setText("");
firstFilled=false;
enter.addActionListener(new ActionListener()
public void actionPerformed(ActionEvent e)
double result;
String answer="";
String number = display.getText();
dNum2 = Double.parseDouble(number);
dNum1=Double.parseDouble(number);
switch(op)
case ADD:
result = dNum1 + dNum2;
break;
case SUB:
result = dNum1 - dNum2;
break;
case MUL:
result = dNum1 * dNum2;
break;
case DIV:
result = dNum1 / dNum2;
break;
default:
result= -1.0;
break;
if(result==(int)result)
answer=(new Integer((int)result)).toString();
else
answer=(new Double(result)).toString();
display.setText(answer);
clearScreen=true;
firstFilled=false;
dNum1=0;
dNum2=0;
opPanel.add(clear);
opPanel.add(addition);
opPanel.add(subtraction);
opPanel.add(multiply);
opPanel.add(divide);
opPanel.add(mod);
opPanel.add(enter);
contentPane.add(opPanel, "East");
//Creating the frame object
public class CalculatorMain
public void main(String[] args)
CalculatorFrame cf=new CalculatorFrame();
cf.show();
ERRORS THAT I HAVE!!:
javac calculatorframe.javacalculatorframe.java:150: '(' expected
public void OpActionListener implements ActionListener
^
calculatorframe.java:7: class CalculatorFrame is public, should be declared in a file named CalculatorFrame.java
public class CalculatorFrame extends JFrame
^
calculatorframe.java:54: cannot resolve symbol
symbol : method addOperation ()
location: class CalculatorFrame
addOperation();
^
3 errors
>

Answer 1

Here I did this for someone in the 'new to' forum about 2 weeks back. They had some really awful code they say they got from a java book -cannot recall the author, but I do know his work should be burned and the person executed with a mercy killing (I still haven't recovered from the shock of this and I think most of the regular contributors in these forums could write FAR BETTER books than this clown)
Hmm... I do rant sometimes. Erm, you're welcome - this is their rebuild;-import javax.swing.*;
import java.awt.*;
import java.awt.event.*;
public class Calculator extends JFrame implements ActionListener{
   JButton []buttons = new JButton[25];
     private JTextField display= new JTextField("0.0",12);
   String status = "    Status : ";
   JLabel label = new JLabel(status);
     private double sum    = 0.0d;
     private String nums   = "";
     private double arg    = 0.0d;
     private double tot    = 0.0d;
     private boolean start = true,div,mult,add,sub;
     private String memory = "0";
   java.text.DecimalFormat df=new java.text.DecimalFormat("#,##0.0####");
   Font f = new Font("Times New Roman", Font.BOLD,14);
   Color midBlue  = new Color(20, 15, 140);
public Calculator(){
     super();
     setTitle("Java Calculator");
   JPanel mainPan = new JPanel();
   mainPan.setLayout(new BorderLayout() );
   JPanel textPanel = new JPanel();
   textPanel.setBackground(midBlue);
   textPanel.setLayout(new BorderLayout());
   display.setHorizontalAlignment(JTextField.RIGHT);
   label.setForeground(Color.white);
   display.setFont(new Font("",0,14));
   display.setEditable(false);
   display.setBackground(Color.white);
   label.setFont(new Font("Arial",0,12));
   JPanel emptyPan = new JPanel();
   emptyPan.setBackground(midBlue);
   JPanel emptyP1 = new JPanel();
   emptyP1.setBackground(midBlue);
   JPanel emptyP2 = new JPanel();
   emptyP2.setBackground(midBlue);
   textPanel.add("North", label);
   textPanel.add("Center", display);
   textPanel.add("South",emptyPan );
   textPanel.add("East",emptyP1 );
   textPanel.add("West",emptyP2 );
   JPanel butPanel = new JPanel();
   butPanel.setBackground(midBlue);
   butPanel.setLayout(new GridLayout(5, 5, 10, 10));
   String []str = {"","","","CE","C","1","2","3","/","RM","4","5","6",
                  "*","CM","7","8","9","+","M+","0",".","=","-","M-"};
   for(int j=0; j<25; j++) {
      if(j<3) {
         buttons[j] = new JButton(str[j]);
         butPanel.add(buttons[j]);
      else {
         buttons[j] = new JButton(str[j]);
         buttons[j].addActionListener(this);
         buttons[j].setFont(f);
           buttons[j].setBorder(BorderFactory.createRaisedBevelBorder());
         butPanel.add(buttons[j]);
   JPanel emptyPan1 = new JPanel();
   emptyPan1.setBackground(midBlue);
   JPanel emptyPan2 = new JPanel();
   emptyPan2.setBackground(midBlue);
   JPanel emptyPan3 = new JPanel();
   emptyPan3.setBackground(midBlue);
   mainPan.add("North", textPanel);
   mainPan.add("Center", butPanel);
   mainPan.add("South", emptyPan1);
   mainPan.add("East", emptyPan2);
   mainPan.add("West", emptyPan3);
   getContentPane().add(mainPan);
public void actionPerformed(ActionEvent e){
   String s = e.getActionCommand();
      if ((s.equals("1"))||(s.equals("2"))||(s.equals("3"))||(s.equals("4"))
        ||(s.equals("5"))||(s.equals("6"))||(s.equals("7"))||(s.equals("8"))
        ||(s.equals("9"))||(s.equals("0"))||(s.equals("."))){
           nums += s;
           display.setText(nums);
      if (s.equals("/")){
         arg=Double.parseDouble(display.getText());
         nums="";
         div=true;
      if (s.equals("*")){
         arg=Double.parseDouble(display.getText());
         nums="";
         mult=true;
      if (s.equals("-")){
         arg=Double.parseDouble(display.getText());
         nums="";
         sub=true;
      if (s.equals("+")){
         arg=Double.parseDouble(display.getText());
         nums="";
         add=true;
      if (s.equals("=")){
         tot=Double.parseDouble(display.getText());
         if(div)tot=arg/tot;
         if(mult)tot=arg*tot;
         if(add)tot=arg+tot;
         if(sub)tot=arg-tot;
         display.setText(df.format(tot));
         div=mult=sub=add=false;
public static void main(String[] args){
    Calculator frame = new Calculator();
    frame.setVisible(true);
    frame.setDefaultCloseOperation( EXIT_ON_CLOSE );
      Image onFrame = Toolkit.getDefaultToolkit().getImage("flag.gif") ;
    frame.setIconImage(onFrame);
    frame.setLocation(300, 240);
    frame.setResizable(false);
    frame.pack();
}