Tabbed pane problem

[HxRLxY]

I posted a different question (Help with non-static/static problem) which was answered. I changed my inner class to a static nested class, but now I cannot create an object using that class and add it to the JTabbedPane. I get a 'cannot find symbol' error, and it points to the pane.addTab method. The program works fine when I remove the nested class and make it a separate class, then instantiate it. Any help would be greatly appreciated.

Here is my source code:

import javax.swing.*;
   import javax.swing.JOptionPane.*;
   import javax.swing.JTabbedPane.*;
   import java.awt.*;
   import java.awt.event.*;
 
    public class WeightConverter extends JPanel{
 
          //main method will instantiate and display GUI
 
       public static void main(String[] args){
 
         JFrame frame = new JFrame("Weight Converter");
         frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
 
         JTabbedPane pane = new JTabbedPane();
         ConvertToOuncesPane panel_1 = new ConvertToOuncesPane();   
 
         pane.addTab("Convert", panel_1);
 
         frame.getContentPane().add(pane);
         frame.pack();
         frame.setVisible(true);
      }
      //ConvertToOuncesPane class will create the pane for converting to ounces. 
       static class ConvertToOuncesPane{
 
          //Set up new component identifiers
         JLabel tonsLabel, stonesLabel, poundsLabel, ouncesLabel, resultLabel;
         JTextField tonsField, stonesField, poundsField, ouncesField;
         JButton btnConvert, btnClear, btnExit;
         String resultString = "Total Number of Ounces: ";
 
          /*****************************************************************************\
          |
          |this method will be the primary constructor method for the class
          |
          \*****************************************************************************/
          public ConvertToOuncesPane(){
 
             //set up the labels for the input boxes
            tonsLabel = new JLabel("Enter number of tons:");
            stonesLabel = new JLabel("Enter number of stones:");
            poundsLabel = new JLabel("Enter number of pounds:");
            ouncesLabel = new JLabel("Enter number of pounds:");
            resultLabel = new JLabel(resultString + "---");
 
             //set up the input boxes
            tonsField = new JTextField(10);
            stonesField = new JTextField(10);
            poundsField = new JTextField(10);
            ouncesField = new JTextField(10);
 
             //set up the convert button and add action listener
            btnConvert = new JButton("Convert");
            btnConvert.addActionListener (new ConvertToListener());
 
             //set up the clear button and add action listener
            btnClear = new JButton("Clear");
            btnClear.addActionListener (new ClearToListener());
 
             //set up the exit button and add action listener
            btnExit = new JButton("Exit");
            btnExit.addActionListener (new ExitToListener());
 
             //add components to the pane
            JPanel panel = new JPanel();
            panel.add (tonsLabel);
            panel.add (tonsField);
            panel.add (stonesLabel);
            panel.add (stonesField);
            panel.add (poundsLabel);
            panel.add (poundsField);
            panel.add (ouncesLabel);
            panel.add (ouncesField);
            panel.add (resultLabel);
            panel.add (btnConvert);
            panel.add (btnClear);
            panel.add (btnExit);
 
             //set default values for textFields
            tonsField.setText("0");
            stonesField.setText("0");
            poundsField.setText("0");
            ouncesField.setText("0");
 
             //set up the look of the pane
            panel.setBackground(Color.white);
            panel.setPreferredSize(new Dimension(200, 280));
 
 
 
         }
 
        /**********************************************************************\
        |
        |the ConvertToListener class is dedicated to the convert button 
        |on the Convert To Ounces Pane
        |
        \**********************************************************************/ 
          private class ConvertToListener implements ActionListener{
 
             public void actionPerformed(ActionEvent event){
 
                //set up variables for the ConvertListener class
               int tons = 0, stones = 0, pounds = 0, ounces = 0, totalOunces = 0;
               final int CONVERT_TONS = 32000, CONVERT_STONES = 224, CONVERT_POUNDS = 16;
               String errorMessage = "You must enter a number.";
               boolean testField;
 
                //collect, test, and parse integers from each textField
                   //test tonsField
               testField = testInt(tonsField.getText());
 
               if (testField == true)
                  tons = Integer.parseInt(tonsField.getText());
               else
                  JOptionPane.showMessageDialog(null, errorMessage);
 
                    //test stonesField
               testField = testInt(stonesField.getText());
 
               if (testField == true)
                  stones = Integer.parseInt(stonesField.getText());
               else
                  JOptionPane.showMessageDialog(null, errorMessage);
 
                    //test poundsField
               testField = testInt(poundsField.getText());
 
               if (testField == true)
                  pounds = Integer.parseInt(poundsField.getText());
               else
                  JOptionPane.showMessageDialog(null, errorMessage);
 
                    //test ouncesField
               testField = testInt(ouncesField.getText());
 
               if (testField == true)
                  ounces = Integer.parseInt(ouncesField.getText());
               else
                  JOptionPane.showMessageDialog(null, errorMessage);
 
                //perform the conversion calculation
               totalOunces = tons * CONVERT_TONS + stones * CONVERT_STONES + pounds * CONVERT_POUNDS + ounces;
 
                //display the result
               resultLabel.setText(resultString + totalOunces);    
            }
 
             //set up a try-catch in the event a letter is entered into a field
             boolean testInt(String test){
               try{
                  Integer.parseInt(test);
               }
                   catch(NumberFormatException exception){
                     return false;
                  }
               return true;
            }
 
 
 
 
         }
         /***************************************************************************\
          |
          |the ClearToListener class is dedicated to the Clear button on 
          |the Convert To Ounces Pane
          |
          \***************************************************************************/
          private class ClearToListener implements ActionListener{
 
              /****************************************************************\
              |
              |this method will restore the default zeros to all text fields
              |
              \****************************************************************/
             public void actionPerformed(ActionEvent event){
                 //restore default values to textFields
               tonsField.setText("0");
               stonesField.setText("0");
               poundsField.setText("0");
               ouncesField.setText("0");
 
            }
         }
         /*******************************************************************************\
          |
          |the ExitToListener class is dedicated to the Exit button on the
          |Convert To Ounces Pane
          |
          \*******************************************************************************/
 
          private class ExitToListener implements ActionListener{
             /***********************************************************\
             |
             |this method will end the program when the user 
             |clicks the exit button
             |
             \***********************************************************/    
             public void actionPerformed(ActionEvent event){
               System.exit(0);
            }
         }
 
      }
 
 
 
 
   }
 

[Laharl]

The program works fine when I remove the nested class and make it a separate class, then instantiate it.

Sounds to me like you've solved your own problem.

[HxRLxY]

Sounds to me like you've solved your own problem.

The only problem with that solution is that the program is a lab project and must be submitted as one file. So I can't write a separate class file, I have to have them all nested.

[Laharl]

Rather than placing the second class in a separate file, keep it in the same file. A file may have multiple classes, but only one public class. Thus, simply omit the public keyword from the definition of the second class.

[HxRLxY]

Rather than placing the second class in a separate file, keep it in the same file. A file may have multiple classes, but only one public class. Thus, simply omit the public keyword from the definition of the second class.

I removed the second class from the primary class as you suggested. But I still get the cannot find symbol error at pane.addTab("Co nvert", panel_1) . I can add the tab if I use a JComponent (e.g. JButton), but I cant add the panel_1 object. Any ideas?

[Laharl]

Your ConvertToOunces Pane class is not a JComponent, so it can't be added as a tab. You need to extend JComponent and implement any necessary methods (I don't think there are any, but if there are the compiler will tell you when you don't).

[HxRLxY]

Well, I finally figured it out. I was missing an extends JPanel modifier. Thanks for the help.

[JosAH]

Well, I finally figured it out. I was missing an extends JPanel modifier. Thanks for the help.

That's what I wrote already in your other thread. You should
read the answers given to you.

kind regards,

Jos