ClassCastException when reading from binary file

Question

I get a java.lang.ClassCastException while reading a binary file with a generic method. I was trying to read two diferent files with the same method but then I get the exception and I dont know why.

This is the code in the method generic for read the file: Read is a method part of the Class ReadBenary.

 import java.io.ObjectInputStream;
 import java.io.FileInputStream;
 import java.io.IOException;

 public class ReadBinary{

private ObjectInputStream reader;

public boolean open(String name) {
    try {
        reader= new ObjectInputStream(new FileInputStream(name));
        return true;
    } catch (IOException exception) {
        System.err.println("Error");
        return false;
    }
}

public void close() {
    try {
        if (reader != null) {
            lector.close();
        }
    } catch (IOException exception) {
        System.err.println("Error");
    }
}

public <E> E read() {

    E object = null;
    try {
        object = (E) reader.readObject();
    } catch (ClassNotFoundException ex) {
        System.err.println("Class dont found");
        System.err.println(ex);
    } catch (IOException ex) {
        System.err.println("End of the file");
        System.err.println(ex);
    } catch (ClassCastException ex) {
        System.err.println("Class dont found");
    }
    return object;
}

This is the code in the main:

 ReadBinary reader= new ReadBinary();

      if (reader.open(file3)) {
      *  Bill bill = reader.read();
        while (bill != null) {
            manejadorBill.insert(bill);
            bill = reader.read();
        }
        reader.close();
       }

    if (reader.open(file1)) {
        Customer customer= reader.read();
        while (customer != null) {
            manejadorCustomer.insert(customer);
            customer = reader.read();
        }
        reader.close();
    }

This is the method that write the objects in the file:

public <E> void escribir(E objeto) {
    try {
        escritor.writeObject(objeto);
    } catch (IOException exception) {
        System.err.print("Error rawr");
    }
}

Bill and Customer are two independent class. When i try to run the program it says that Customer cant be cast as Bill.

It says that the error occurs in the line with *.

Answer 1

It seems that you don't have Bill objects in file3. To check this change read() to:

public <E> E read() {
    Objject obj;
    E object = null;
    try {
          obj = reader.readObject();
          System.out.println(obj.getClass().getName())       
          object = (E) obj;
    } catch (ClassNotFoundException ex) {
        System.err.println("Class dont found");
        System.err.println(ex);
    } catch (IOException ex) {
        System.err.println("End of the file");
        System.err.println(ex);
    } catch (ClassCastException ex) {
        System.err.println("Class dont found");
    }
    return object;
}

to see what are actual types.

Answer 2

The ClassCastException means that the next object written to the stream was not in fact a Bill. Check the code that writes the objects, to see what types of objects it is in fact writing. Some System.out.printlns might be helpful to see exactly what is being written.