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Thread: Help codiing calculator

  1. June 4th, 2009, 04:16 PM #1
    FM010
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    Default Help codiing calculator

    I am trying to code a calculator using java but every time the = button is pressed a number format exception crops up. Can anyone see what's wrong in the code please ? Thanks
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  3. June 5th, 2009, 02:09 AM #2
    JavaPF
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    Default Re: Help codiing calculator

    Hello FM010, welcome to the Java Programming Forums

    It's something to do with your String s.charAt() I think.

    There is a String Index Out of Bounds exception.

    The charAt() method returns a character value for the character at the given position of the String. This exception is telling us that you are trying to access a position that does not exist.
    Please use [highlight=Java] code [/highlight] tags when posting your code.
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  4. June 5th, 2009, 03:12 AM #3
    Freaky Chris
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    Default Re: Help codiing calculator 

    int a = s.charAt(i);
...
if(s.chatAt(a)){
   ...
}

    This is your problem as JAvaPF stated its an out of range exception. the reason for it is when you do this s.charAt(i); you are expecting a value such as 3 to be assigned to a. where as what you actually get is the ascii code for the number 3 which is infact 51. So then you try and access the character at s51 which more that likely doesn't exist.

    EDIT: JavaPF did mention about the character ascii value being returned, i just missed it. Wasted post, sorry

    Hope that helps.
    Regards,
    Chris
    Last edited by Freaky Chris; June 5th, 2009 at 05:16 AM.
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  5. June 7th, 2009, 10:08 AM #4
    FM010
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    Default Re: Help codiing calculator

    Thanks a lot your post was very useful. I am still having some trouble because a string index ou of bounds exception is cropping up.

    Thanks
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  6. June 7th, 2009, 11:13 AM #5
    JavaPF
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    Default Re: Help codiing calculator

    Can you please post all of your code. I will take a look for you...

    Make sure you paste the code within code tags. Check my signature if you are unsure.
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  7. June 9th, 2009, 03:37 PM #6
    FM010
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    Default Re: Help codiing calculator

    This is the code. Thanks for your help. 

     public class Calculator extends javax.swing.JFrame {
 
    /** Creates new form Calculator */
    public Calculator() {
        initComponents();
    }
 
    /** This method is called from within the constructor to
     * initialize the form.
     * WARNING: Do NOT modify this code. The content of this method is
     * always regenerated by the Form Editor.
     */
    // <editor-fold defaultstate="collapsed" desc="Generated Code">                          
    private void initComponents() {
 
        calculatorPanel = new javax.swing.JPanel();
        num1Button = new javax.swing.JButton();
        num4Button = new javax.swing.JButton();
        num3Button = new javax.swing.JButton();
        num2Button = new javax.swing.JButton();
        num5Button = new javax.swing.JButton();
        num6Button = new javax.swing.JButton();
        num7Button = new javax.swing.JButton();
        num8Button = new javax.swing.JButton();
        num9Button = new javax.swing.JButton();
        num0Button = new javax.swing.JButton();
        displayScreen = new javax.swing.JTextField();
        equalsButton = new javax.swing.JButton();
        plusButton = new javax.swing.JButton();
        minusButton = new javax.swing.JButton();
        multiplicationButton = new javax.swing.JButton();
        divisionButton = new javax.swing.JButton();
 
        setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE);
 
        calculatorPanel.setBorder(javax.swing.BorderFactory.createLineBorder(new java.awt.Color(0, 0, 0)));
 
        num1Button.setText("1");
        num1Button.addMouseListener(new java.awt.event.MouseAdapter() {
            public void mouseReleased(java.awt.event.MouseEvent evt) {
                num1ButtonMouseReleased(evt);
            }
        });
 
        num4Button.setText("4");
        num4Button.addMouseListener(new java.awt.event.MouseAdapter() {
            public void mouseReleased(java.awt.event.MouseEvent evt) {
                num4ButtonMouseReleased(evt);
            }
        });
 
        num3Button.setText("3");
        num3Button.addMouseListener(new java.awt.event.MouseAdapter() {
            public void mouseReleased(java.awt.event.MouseEvent evt) {
                num3ButtonMouseReleased(evt);
            }
        });
 
        num2Button.setText("2");
        num2Button.addMouseListener(new java.awt.event.MouseAdapter() {
            public void mouseReleased(java.awt.event.MouseEvent evt) {
                num2ButtonMouseReleased(evt);
            }
        });
 
        num5Button.setText("5");
        num5Button.addMouseListener(new java.awt.event.MouseAdapter() {
            public void mouseReleased(java.awt.event.MouseEvent evt) {
                num5ButtonMouseReleased(evt);
            }
        });
 
        num6Button.setText("6");
        num6Button.addMouseListener(new java.awt.event.MouseAdapter() {
            public void mouseReleased(java.awt.event.MouseEvent evt) {
                num6ButtonMouseReleased(evt);
            }
        });
 
        num7Button.setText("7");
        num7Button.addMouseListener(new java.awt.event.MouseAdapter() {
            public void mouseReleased(java.awt.event.MouseEvent evt) {
                num7ButtonMouseReleased(evt);
            }
        });
 
        num8Button.setText("8");
        num8Button.addMouseListener(new java.awt.event.MouseAdapter() {
            public void mouseReleased(java.awt.event.MouseEvent evt) {
                num8ButtonMouseReleased(evt);
            }
        });
 
        num9Button.setText("9");
        num9Button.addMouseListener(new java.awt.event.MouseAdapter() {
            public void mouseReleased(java.awt.event.MouseEvent evt) {
                num9ButtonMouseReleased(evt);
            }
        });
 
        num0Button.setText("0");
        num0Button.addMouseListener(new java.awt.event.MouseAdapter() {
            public void mouseReleased(java.awt.event.MouseEvent evt) {
                num0ButtonMouseReleased(evt);
            }
        });
 
        displayScreen.addActionListener(new java.awt.event.ActionListener() {
            public void actionPerformed(java.awt.event.ActionEvent evt) {
                displayScreenActionPerformed(evt);
            }
        });
 
        equalsButton.setText("=");
        equalsButton.addMouseListener(new java.awt.event.MouseAdapter() {
            public void mouseReleased(java.awt.event.MouseEvent evt) {
                equalsButtonMouseReleased(evt);
            }
        });
 
        plusButton.setText("+");
        plusButton.addMouseListener(new java.awt.event.MouseAdapter() {
            public void mouseReleased(java.awt.event.MouseEvent evt) {
                plusButtonMouseReleased(evt);
            }
        });
 
        minusButton.setText("-");
        minusButton.addMouseListener(new java.awt.event.MouseAdapter() {
            public void mouseReleased(java.awt.event.MouseEvent evt) {
                minusButtonMouseReleased(evt);
            }
        });
 
        multiplicationButton.setText("*");
        multiplicationButton.addMouseListener(new java.awt.event.MouseAdapter() {
            public void mouseReleased(java.awt.event.MouseEvent evt) {
                multiplicationButtonMouseReleased(evt);
            }
        });
 
        divisionButton.setText("/");
        divisionButton.addMouseListener(new java.awt.event.MouseAdapter() {
            public void mouseReleased(java.awt.event.MouseEvent evt) {
                divisionButtonMouseReleased(evt);
            }
        });
 
        javax.swing.GroupLayout calculatorPanelLayout = new javax.swing.GroupLayout(calculatorPanel);
        calculatorPanel.setLayout(calculatorPanelLayout);
        calculatorPanelLayout.setHorizontalGroup(
            calculatorPanelLayout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(calculatorPanelLayout.createSequentialGroup()
                .addGap(29, 29, 29)
                .addGroup(calculatorPanelLayout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                    .addComponent(displayScreen, javax.swing.GroupLayout.PREFERRED_SIZE, 204, javax.swing.GroupLayout.PREFERRED_SIZE)
                    .addGroup(calculatorPanelLayout.createSequentialGroup()
                        .addGroup(calculatorPanelLayout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                            .addGroup(calculatorPanelLayout.createSequentialGroup()
                                .addComponent(num1Button)
                                .addGap(18, 18, 18)
                                .addComponent(num2Button)
                                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
                                .addComponent(num3Button))
                            .addGroup(calculatorPanelLayout.createSequentialGroup()
                                .addComponent(num4Button)
                                .addGap(18, 18, 18)
                                .addComponent(num5Button)
                                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
                                .addComponent(num6Button))
                            .addGroup(calculatorPanelLayout.createSequentialGroup()
                                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                                .addComponent(num7Button)
                                .addGap(18, 18, 18)
                                .addGroup(calculatorPanelLayout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                                    .addComponent(num0Button)
                                    .addGroup(calculatorPanelLayout.createSequentialGroup()
                                        .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                                        .addComponent(num8Button)
                                        .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
                                        .addComponent(num9Button)))))
                        .addGap(50, 50, 50)
                        .addGroup(calculatorPanelLayout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                            .addComponent(equalsButton)
                            .addGroup(calculatorPanelLayout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                                .addComponent(divisionButton, 0, 0, Short.MAX_VALUE)
                                .addGroup(calculatorPanelLayout.createParallelGroup(javax.swing.GroupLayout.Alignment.TRAILING, false)
                                    .addComponent(minusButton, javax.swing.GroupLayout.Alignment.LEADING, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                                    .addComponent(plusButton, javax.swing.GroupLayout.Alignment.LEADING, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                                    .addComponent(multiplicationButton, 0, 0, Short.MAX_VALUE))))))
                .addContainerGap(77, Short.MAX_VALUE))
        );
        calculatorPanelLayout.setVerticalGroup(
            calculatorPanelLayout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(calculatorPanelLayout.createSequentialGroup()
                .addGap(32, 32, 32)
                .addComponent(displayScreen, javax.swing.GroupLayout.PREFERRED_SIZE, 37, javax.swing.GroupLayout.PREFERRED_SIZE)
                .addGap(18, 18, 18)
                .addGroup(calculatorPanelLayout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                    .addComponent(num1Button)
                    .addComponent(num2Button)
                    .addComponent(num3Button)
                    .addComponent(plusButton))
                .addGroup(calculatorPanelLayout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                    .addGroup(calculatorPanelLayout.createSequentialGroup()
                        .addGap(6, 6, 6)
                        .addComponent(minusButton)
                        .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                        .addComponent(multiplicationButton)
                        .addGroup(calculatorPanelLayout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
                            .addGroup(calculatorPanelLayout.createSequentialGroup()
                                .addGap(40, 40, 40)
                                .addComponent(num0Button))
                            .addGroup(calculatorPanelLayout.createSequentialGroup()
                                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                                .addComponent(divisionButton)
                                .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.RELATED)
                                .addComponent(equalsButton))))
                    .addGroup(calculatorPanelLayout.createSequentialGroup()
                        .addGap(18, 18, 18)
                        .addGroup(calculatorPanelLayout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                            .addComponent(num4Button)
                            .addComponent(num5Button)
                            .addComponent(num6Button))
                        .addPreferredGap(javax.swing.LayoutStyle.ComponentPlacement.UNRELATED)
                        .addGroup(calculatorPanelLayout.createParallelGroup(javax.swing.GroupLayout.Alignment.BASELINE)
                            .addComponent(num7Button)
                            .addComponent(num8Button)
                            .addComponent(num9Button))))
                .addContainerGap(220, Short.MAX_VALUE))
        );
 
        javax.swing.GroupLayout layout = new javax.swing.GroupLayout(getContentPane());
        getContentPane().setLayout(layout);
        layout.setHorizontalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addGap(46, 46, 46)
                .addComponent(calculatorPanel, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                .addContainerGap())
        );
        layout.setVerticalGroup(
            layout.createParallelGroup(javax.swing.GroupLayout.Alignment.LEADING)
            .addGroup(layout.createSequentialGroup()
                .addContainerGap()
                .addComponent(calculatorPanel, javax.swing.GroupLayout.DEFAULT_SIZE, javax.swing.GroupLayout.DEFAULT_SIZE, Short.MAX_VALUE)
                .addContainerGap())
        );
 
        pack();
    }// </editor-fold>                        
 
    private void displayScreenActionPerformed(java.awt.event.ActionEvent evt) {                                              
 
}                                             
 
    private void num1ButtonMouseReleased(java.awt.event.MouseEvent evt) {                                         
              displayScreen.setText(displayScreen.getText()+ num1Button.getText());   
    }                                        
 
    private void num2ButtonMouseReleased(java.awt.event.MouseEvent evt) {                                         
       displayScreen.setText(displayScreen.getText()+ num2Button.getText()); // TODO add your handling code here:
    }                                        
 
    private void equalsButtonMouseReleased(java.awt.event.MouseEvent evt) {                                           
       int i=0;
       String s= displayScreen.getText();
        String num1= " ";
        String num2= " ";
        String res= " ";
        char achar=' ';
 
        int stringLength= s.length();
        char valueChar=(char) stringLength;
        int value= (int) valueChar;
 
       while(i!=value){
 
 
 
 
 
       do
       {
       		int charValue= s.charAt(i);
                achar= (char) charValue;
 
            num1=num1 + achar;
            i++;
 
 
      } while(( achar!='+')||(achar!='-')||(achar!='*')||(achar!='/'));
 
       int number1= Integer.parseInt(num1);
 
 
 
 
        int a=s.charAt(i-1);
        char operator= (char) a;
 
 
        while (i!=value)
        {
        	int charValue= s.charAt(i);
        	char charPosition= (char) charValue;
 
            num2=num2+achar;
            i++;
        }
 
        int number2=Integer.parseInt(num2);
 
 
        if (operator=='+')
        {
            int result= number1+number2;
            res= " "+result;
            displayScreen.setText(res);
        }
 
         if (s.charAt(a)=='-')
        {
            int result= number1-number2;
            res= " "+result;
            displayScreen.setText(res);
        }
 
         if (operator=='*')
        {
            int result= number1*number2;
            res= " "+result;
            displayScreen.setText(res);
        }
 
         if (operator=='/')
        {
            int result= number1/number2;
            res= " "+result;
            displayScreen.setText(res);
        }
 
 
        num1= res;
      } 
    }                                          
 
    private void plusButtonMouseReleased(java.awt.event.MouseEvent evt) {                                         
       displayScreen.setText(displayScreen.getText()+ plusButton.getText()); // TODO add your handling code here:
    }                                        
 
    private void num3ButtonMouseReleased(java.awt.event.MouseEvent evt) {                                         
       displayScreen.setText(displayScreen.getText()+ num3Button.getText());  // TODO add your handling code here:
    }                                        
 
    private void num4ButtonMouseReleased(java.awt.event.MouseEvent evt) {                                         
      displayScreen.setText(displayScreen.getText()+ num4Button.getText());   // TODO add your handling code here:
    }                                        
 
    private void num5ButtonMouseReleased(java.awt.event.MouseEvent evt) {                                         
        displayScreen.setText(displayScreen.getText()+ num5Button.getText()); // TODO add your handling code here:
    }                                        
 
    private void num6ButtonMouseReleased(java.awt.event.MouseEvent evt) {                                         
       displayScreen.setText(displayScreen.getText()+ num6Button.getText());  // TODO add your handling code here:
    }                                        
 
    private void num7ButtonMouseReleased(java.awt.event.MouseEvent evt) {                                         
       displayScreen.setText(displayScreen.getText()+ num7Button.getText());  // TODO add your handling code here:
    }                                        
 
    private void num8ButtonMouseReleased(java.awt.event.MouseEvent evt) {                                         
       displayScreen.setText(displayScreen.getText()+ num8Button.getText());  // TODO add your handling code here:
    }                                        
 
    private void num9ButtonMouseReleased(java.awt.event.MouseEvent evt) {                                         
        displayScreen.setText(displayScreen.getText()+ num9Button.getText()); // TODO add your handling code here:
    }                                        
 
    private void num0ButtonMouseReleased(java.awt.event.MouseEvent evt) {                                         
       displayScreen.setText(displayScreen.getText()+ num0Button.getText());  // TODO add your handling code here:
    }                                        
 
    private void minusButtonMouseReleased(java.awt.event.MouseEvent evt) {                                          
        displayScreen.setText(displayScreen.getText()+ minusButton.getText()); // TODO add your handling code here:
    }                                         
 
    private void multiplicationButtonMouseReleased(java.awt.event.MouseEvent evt) {                                                   
        displayScreen.setText(displayScreen.getText()+ multiplicationButton.getText()); // TODO add your handling code here:
    }                                                  
 
    private void divisionButtonMouseReleased(java.awt.event.MouseEvent evt) {                                             
       displayScreen.setText(displayScreen.getText()+ divisionButton.getText());  // TODO add your handling code here:
    }                                            
 
    /**
     * @param args the command line arguments
     */
    public static void main(String args[]) {
        java.awt.EventQueue.invokeLater(new Runnable() {
            public void run() {
                new Calculator().setVisible(true);
            }
        });
    }
 
    // Variables declaration - do not modify                     
    private javax.swing.JPanel calculatorPanel;
    private javax.swing.JTextField displayScreen;
    private javax.swing.JButton divisionButton;
    private javax.swing.JButton equalsButton;
    private javax.swing.JButton minusButton;
    private javax.swing.JButton multiplicationButton;
    private javax.swing.JButton num0Button;
    private javax.swing.JButton num1Button;
    private javax.swing.JButton num2Button;
    private javax.swing.JButton num3Button;
    private javax.swing.JButton num4Button;
    private javax.swing.JButton num5Button;
    private javax.swing.JButton num6Button;
    private javax.swing.JButton num7Button;
    private javax.swing.JButton num8Button;
    private javax.swing.JButton num9Button;
    private javax.swing.JButton plusButton;
    // End of variables declaration                   
 
}
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  9. June 10th, 2009, 09:04 AM #7
    JavaPF
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    Default Re: Help codiing calculator

    Your problem is with int = 0; in the equalsButtonMouseReleased(java.awt.event.MouseEven t evt) method.
    Please use [highlight=Java] code [/highlight] tags when posting your code.
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  10. June 12th, 2009, 02:25 PM #8
    FM010
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    Default Re: Help codiing calculator

    Is there any way how I could solve the problem please ?

    Thanks
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