Help With an error

[tyczj]

i am some what new to java so i am not really familiar with all the errors and such but i am getting one that says this:

Exception in thread "main" java.lang.ClassCastException: lab8ab.EmployeeAryApplicEx cannot be cast to lab8ab.EmployeeMultiTypeSeqFileExer
        at lab8ab.EmployeeMultiTypeOpenListener.<init>(EmployeeMultiTypeOpenListener.java:22)
        at lab8ab.EmployeeAryApplicEx.<init>(EmployeeAryApplicEx.java:115)
        at lab8ab.EmployeeAryApplicEx.main(EmployeeAryApplicEx.java:43)

what does that mean?

the program is suppose to be able to save and open a file of employees

[jwenting]

says it all, you're trying to cast something to something else that it can't be cast to.

[tyczj]

but what does casting mean and y would i noe be able to cast it?

[jwenting]

see the Sun Java tutorial.

[javaAddict]

You are trying to turn a EmployeeAryApplicEx instance into a EmployeeMultiTypeSeqFileExer, which cannot be done. I presume that you wrote something like this:

EmployeeAryApplicEx empAryApplicEx=new EmployeeAryApplicEx();
EmployeeMultiTypeSeqFile empMultiTypeSeqFileExer=new EmployeeMultiTypeSeqFileExer();
empMultiTypeSeqFileExer = (EmployeeMultiTypeSeqFile)empAryApplicEx;

What you did is like trying to cast a String into an Integer:

String s="3";
Integer integ=(Integer)s;

Which cannot be done in both cases because the objects are not of the same type.
It would have worked if one object extended the other

[tyczj]

makes sense but where the error takes you to is a part where my teacher gave us code and we had to expand on it. the code worked fine then and i made no changes to that part

My EmployeeMultiTypeOpenListener: error line in red

package lab8ab;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.io.*;
import java.text.*;

// Purpose:  To handle an event caused by user selection of Open action from GUI
public class EmployeeMultiTypeOpenListener implements ActionListener  {
   private EmployeeMultiTypeSeqFileExer fr;    // Hold reference to JFrame subclass instance
   private DataInputStream input;    // Stream for inputting data from file
   private File selectedFile;        // The file selected by user
   private String path = "C:\\";     // Path for file selection dialog

   // Constructor
   public EmployeeMultiTypeOpenListener( JFrame f, String pt ) {
      fr = (EmployeeMultiTypeSeqFileExer)f;
      path = pt;
   }

   //  Perform action using the file Open operation selected by user from menu
   public void actionPerformed( ActionEvent e ) {

      JFileChooser JFChoose = new JFileChooser(path);
      int result = JFChoose.showOpenDialog( fr );
      selectedFile = JFChoose.getSelectedFile();

      // Respond to a user press of the Cancel button
      if ( result == JFileChooser.CANCEL_OPTION )
         return;

      try { // try to create an object representing the user-selected file
         input = new DataInputStream( new FileInputStream( selectedFile ) );
      }
      catch ( Exception ex )  {
          System.out.println( "\nIn FileOpenHandlerM, Open try block: " + ex.toString() );
      }

      try { // try to read the file and create a string consisting of its contents
         char ch;
         fr.setEmployeeCount( 0 );
         String name;
         int idNumber = 0;
         String empType = null;
         String department = null;
         double payRate = 0;
         double hoursWorked;

         do { // read data from the file until end of file is reached
            name = "";
            ch = input.readChar();
            while ( ch != ';' ) {
               name = name + ch;
               ch = input.readChar();
            }
            while (ch != ';'){
               idNumber = idNumber + ch;
                idNumber = input.readInt();
            }
            
            while (ch != ';'){
                empType = empType + ch;
                ch = input.readChar();
            }
            
            while (ch != ';'){
                department = department + ch;
                ch = input.readChar();
            }
            
            while (ch != ';'){
                payRate = payRate + ch;
                payRate = input.readDouble();
            }
            hoursWorked = input.readDouble();
            fr.addEmployeeToArray( idNumber, name, empType, department, payRate, hoursWorked );
         } while ( true );
      }
      catch ( Exception ex ) {
         System.out.println( "\nIn FileOpenHandler, Read try block: " + ex.toString() );
      }

      //fr.setMessageToUser( "Opened and read the file:   " + selectedFile.getName() );
      fr.displayEmployeeData();

      try { // try to close the file
         input.close();
      }
      catch ( Exception ex ) {
         System.out.println( "\nIn FileOpenHandler, Close try block: " + ex.toString() );
      }
   }
}

My EmployeeAryApplicEx: error lines in red

package lab8ab;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.border.*;
import java.io.*;

public class EmployeeAryApplicEx extends JFrame { 
    private String docPath = "C:\\Documents and Settings\\grupka\\My Documents\\";
    // Prompts for user input
    private JLabel label1, label2, label3, label4, label6, label7, label8, label9;
    // Mechanisms for user input
    private JTextField textfield1, textfield2, textfield3, textfield4, textfield5, textfield6;
    private JComboBox typeJCB1,typeJCB2;  // The JComboBox for type selection
    private JButton openButton, // Button to initiate an open file action
             saveButton, // Button to initiate a save file action
             saveTextButton; // Button to initiate an action to save text version
        
    // Mechanism for output display
    private JTextArea textDisplay;        // Output display area
    private int textDisplayWidth = 25;    // Width of the JTextArea
    private int textDisplayHeight = 18;   // Height of the JTextArea
    private boolean cannotAddFlag = false; // Indicates whether employee can be added
    
    private final int MAX_EMPLOYEES = 10;  // The maximum number of employees allowed
    private int countEmployees = 0;        // The number of employees added to array
    private String pRate = "";
    private String hr = "";
    private Employee employeeArray [] = new Employee[MAX_EMPLOYEES];
    
    private String typeNames[] = {"Hourly","Salaried","Union"};
    private String selectedType = "";
    private String depName[] = {"Customer Service","Drafting","Engineering","Quality Control","Sales","Shipping"};
    private String depN = "";
    
    // The main method required for an application program
    public static void main( String[] args )  {
        JFrame frame =  new EmployeeAryApplicEx( ); // Construct the window
        frame.setSize( new Dimension( 360, 470 ) );     // Set its size
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setVisible( true );   // Make the window visible
    }
    
    public EmployeeAryApplicEx() {
        super("XYZ CORPORATION EMPLOYEES");
              setLayout( new BorderLayout() );
        
        JPanel jpan = new JPanel();
        jpan.setLayout(new GridLayout(8,2));
        jpan.setBorder(new EtchedBorder());
        add(jpan,BorderLayout.NORTH);
        
        // Create prompt and input mechanism to get employee number from user
        label1 = new JLabel("Number of Employees:");
        jpan.add( label1);  
        textfield1 = new JTextField( 3 );
        textfield1.setEditable(false);
        textfield1.setText(Integer.toString(countEmployees));
        jpan.add( textfield1 );  // put input JTextField on JPanel
        
        label2 = new JLabel("Max # of Employees:");
        jpan.add( label2 );  
        textfield2 = new JTextField( 3);
        textfield2.setText(Integer.toString(MAX_EMPLOYEES));
        textfield2.setEditable(false);
        jpan.add( textfield2 );  // put input JTextField on JPanel
        
        // Create prompt and input mechanism to get employee type from user
        label6 = new JLabel("Employee Type:");
        jpan.add( label6 );  
        typeJCB1 = new JComboBox(typeNames);
        typeJCB1.setMaximumRowCount(3);
        jpan.add( typeJCB1 );  // put input JTextField on JPanel
        
        label7 = new JLabel("Employee Department");
        jpan.add( label7 );
        typeJCB2 = new JComboBox(depName);
        typeJCB2.setMaximumRowCount(6);
        jpan.add( typeJCB2 );
        
        // Create prompt and input mechanism to get employee name from user
        label3 = new JLabel("Name:");
        jpan.add( label3 );  
        textfield3 = new JTextField( 15 );
        jpan.add( textfield3 );  // put input JTextField on JPanel       
        
        // Create prompt and input mechanism to get employee number from user
        label4 = new JLabel("Employee ID Number:");
        jpan.add( label4 );  
        textfield4 = new JTextField( Integer.toString(countEmployees+2), 15 );
        jpan.add( textfield4 );   // put input JTextField on JPanel    
        
        label8 = new JLabel("Employee Pay Rate $");
        jpan.add(label8);
        textfield5 = new JTextField(9);
        jpan.add (textfield5);
        
        label9 = new JLabel("Hours Worked");
        jpan.add (label9);
        textfield6 = new JTextField(9);
        jpan.add(textfield6);
        
        // Create button panel for file operations
        JPanel buttonPanel = new JPanel();
        buttonPanel.setLayout(new GridLayout(1, 2));
        buttonPanel.setBorder(new TitledBorder("File Operations"));

        // Create button for Open File action, attach ActionListener, add to GUI
        openButton = new JButton("Open File");
        openButton.addActionListener(new EmployeeMultiTypeOpenListener(this, docPath));
        buttonPanel.add(openButton);

        // Create button for Save File action, attach ActionListener, add to GUI
        saveButton = new JButton("Save File");
        saveButton.addActionListener(new EmployeeMultiTypeSaveListener(this, docPath));
        buttonPanel.add(saveButton);

        add(buttonPanel, BorderLayout.SOUTH);

        // Set up JTextArea to display information on all the employees
        textDisplay = new JTextArea( getDataStringAllEmployees(),
                textDisplayHeight,textDisplayWidth);
        textDisplay.setLineWrap( true );
        textDisplay.setWrapStyleWord( true );
        textDisplay.setBorder(new TitledBorder("Employee List"));
        add(textDisplay,BorderLayout.CENTER);
        
        // Listener will respond to a user hitting Enter in any JTextField
        MyActionListener myActListener = new MyActionListener();
        textfield3.addActionListener( myActListener );
        textfield4.addActionListener( myActListener ); 
        textfield5.addActionListener( myActListener );
        textfield6.addActionListener( myActListener );
   
        // Listener will respond to a user selecting from JComboBox
        MyItemListener myItemListener = new MyItemListener();
        typeJCB1.addItemListener(myItemListener); 
        typeJCB2.addItemListener(myItemListener);
        
        // Display data on all Employees in the JTextArea
        displayEmployeeData();
    }    
    
    private void displayEmployeeData(){
        setDisplayFields();
        textDisplay.setText(getDataStringAllEmployees());
    }
    
    // Create and insert the new employee into array

    private void addEmployeeToArray( String id, String nam, String typ, String d, String pRate, String hr){
        if ( countEmployees < MAX_EMPLOYEES ) {
            Employee P = null; //new Employee(nam, Integer.parseInt(id), typ, depN);
            if(typeNames[typeJCB1.getSelectedIndex()].equals(typeNames[0])){
                P = new HourlyEmployee(nam, typ, d, Integer.parseInt(id), Double.parseDouble(pRate), Double.parseDouble(hr));
            }else if(typeNames[typeJCB1.getSelectedIndex()].equals(typeNames[1])){
                P = new SalariedEmployee(nam, typ, d, Integer.parseInt(id), Double.parseDouble(pRate), Double.parseDouble(hr));
            } else {
                P = new UnionEmployee(nam, typ, d, Integer.parseInt(id), Double.parseDouble(pRate), Double.parseDouble(hr));
            }
            employeeArray[countEmployees] = P;
            countEmployees++;
        }
    }

    
    //  Return the employee instance (object) correponding to the pNumb parameter
    private Employee getEmployeeFromArray( int pNumb ) {
        Employee P = null;
        if ( pNumb < countEmployees ) {
            P = employeeArray[pNumb];
        }
        return P;
    }
    
    // Set the contents of the JTextFields
    private void setDisplayFields() {
        textfield1.setText( Integer.toString(countEmployees) );
        textfield2.setText( Integer.toString(MAX_EMPLOYEES) );
        textfield3.setText("");
        textfield4.setText("");
        textfield5.setText("");
        textfield6.setText("");
    }
    
    // Get the string comprised of all the data on all employees
    private String getDataStringAllEmployees() {
        String displayStr = "";
        
        // Add the information on all employees to the display string
        //displayStr = displayStr + "\n  XYZ CORPORATION EMPLOYEES:\n\n ";
        for ( int i = 0; i < countEmployees; i++ ) {
            displayStr += (i+1) + ". " + employeeArray[i].toString() + "\n ";
        }
        if ( cannotAddFlag )
            displayStr += "\nCannot add employees - the array is full\n";
        return displayStr;
    }
    
    class MyActionListener implements ActionListener {
        // Process user's action in JTextField input
        public void actionPerformed(ActionEvent e) {
                if ( countEmployees < MAX_EMPLOYEES )  {                    
                    String name = textfield3.getText();  
                    String idNumber = textfield4.getText();
                    pRate = textfield5.getText();
                    hr = textfield6.getText();
                    addEmployeeToArray(idNumber, name, selectedType, depN, pRate, hr);
                    
                    
                } else {
                    cannotAddFlag = true;
                }                    
                    
            displayEmployeeData();
        }
    }
    
    class MyItemListener implements ItemListener {
        public void itemStateChanged(ItemEvent e) {
            
            // If one of the items in the JComboBox was selected,
            // set the selectedDept variable to the user's selection
            if (e.getSource() == typeJCB1) {
                selectedType = typeNames[typeJCB1.getSelectedIndex()];
            } else if(e.getSource() == typeJCB2) {
                depN = depName[typeJCB2.getSelectedIndex()];
            } 
        }        
    }
}

i did nothing to the error lines which is why im getting confused