Question

This is for a homework I’m doing on my walk learning java.

I’m writing a program and it is all working as expected except the read/write to file.

I have one class named Medico that holds only one string (typeOfMedico) and one int (valorFacturado). Medico is a sub class of Pessoa. Pessoa holds data like name and address. public class Medico extends Pessoa implements Serializable is the main function on Medicoclass.

On my main class, named Clinica, I ask for user input and at the end of I create a new Medico that its added to an Arraylist named medico.

For reading and writing to file I’ve created this class:

package clinica;

import java.io.EOFException;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;

public class FicheiroObjectos {

    private ObjectInputStream iS;
    private ObjectOutputStream oS;

    public void abreLeitura(String nomeDoFicheiro) throws IOException {
        iS = new ObjectInputStream(new FileInputStream(nomeDoFicheiro));
    }

    public void abreEscrita(String nomeDoFicheiro) throws IOException {
        oS = new ObjectOutputStream(new FileOutputStream(nomeDoFicheiro));
    }

    public Object leObjecto() throws IOException, ClassNotFoundException {
        return iS.readObject();
    }

    public void escreveObjecto(Object o) throws IOException {
        oS.writeObject(o);
    }

    public void fechaLeitura() throws IOException {
        iS.close();
    }

    public void fechaEscrita() throws IOException {
        oS.close();
    }

    public void leFicheiroMedicos() {
        Medico medicos;
        while (true) {
            try {
                medicos = (Medico) this.leObjecto();
                Clinica.medicos.add(medicos);
            } catch (EOFException eof) {
                break;
            } catch (ClassNotFoundException cnf) {
                System.out.print("\nClassNotFoundException!\nO programa vai terminar\n");
                System.exit(-1);
            } catch (IOException ioe) {
                System.out.print("\nErro ao ler o ficheiro!\nO programa vai terminar\n");
                System.exit(-1);
            }
        }
    }

    public void escreveFicheiroMedicos() {
        try {
            for (Medico medicos: Clinica.medicos) {
                this.escreveObjecto(medicos);
            }
        } catch (IOException e) {
            System.out.print("\nErro ao escrever no ficheiro!\nO programa vai terminar\n");
            System.exit(-1);
        }
    }
}

On my main class I’ve created this two functions:

 public static void insereDadosExistentes() {

        try {
            FicheiroObjectos file = new FicheiroObjectos();
            file.abreLeitura("Medicos.dat");
            file.leFicheiroMedicos();
            file.fechaLeitura();
        } catch (IOException ioe) {
        }

    }


    public static void gravarMedicos() {

        try {
            FicheiroObjectos file = new FicheiroObjectos();
            file.abreEscrita("Medicos.dat");
            file.escreveFicheiroMedicos();
            file.fechaEscrita();
        } catch (IOException e) {
            System.out.print("\nErro ao escrever no ficheiro!\nO programa vai terminar\n");
            System.exit(-1);
        }

    }
}

Then added insereDadosExistentes() at the beginning of my mainfunction and added gravarMedicos() just after adding a Medico to my medicos arraylist.

When I run my program (On the first run, file Medicos.dat, does not exist) and create a Medico, Medico is added to my arraylist and the file Medicos.dat is created. Then I stop the program and on the next run, which now haves a Medicos.dat file, I get the error:

Erro ao ler o ficheiro!
O programa vai terminar

The problem is in writing the file or reading the file?
I know the error is given when reading the file but it could be because the writhing to file is not properly executed.

If I try to open Medicos.dat I can see some characters but nothing related with the info I input so I don’t even know if the file writing is ok.

Remember that all besides file handling is working as expected.

Can you point me In some directions?

favolas

Answer 1

1. Make sure that you explicitly close the ObjectOutputStream so that all the data is written.

2. Your problem is an IOException. However, the backtrace will tell you what’s going on: trouble opening, reading, what? you can call printStackTrace(), but better you can use a debugging and just look at the stack trace.