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

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

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

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

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