CODEWITHSUNDEEP
javafileobjectinputstream
Hector Mendoza Jacobo
Hector Mendoza Jacobo

Reputation: 149

Exception with ObjectInputStream while reading, and reaching the end of the file

I'm doing a schedule book, and I'm saving a .txt all my objects, that works fine, the problem comes when I read them, my program reads , when the end of the file comes, my program doesn't know what to do, I won't put my code because it's a mess right now, but here's my teacher's code, which is the one that I'm using as a template to do mine:

try{
  //***Instructions for reading***

  //It creates a streamobject with the file's name and asigned format

  FileInputStream fileIn = new FileInputStream("Serializado.txt");

  //It creates an inputobject, so it can represent the object

  ObjectInputStream objIn= new ObjectInputStream(fileIn);

  while (fileIn != null) {

    //with readObject() method,  it extracts the object's content                               

    obInp= (NewAlumno) objIn.readObject(); //Se hace un "cast" a NewAlumno
    System.out.print("Nombre   :" + obInp);
    System.out.print(", Sexo: " + obInp.getSexo());
    System.out.print(", Direccion: "+ obInp.getDireccion());    
    System.out.print(", Promedio: " + obInp.getpromedioPoo());
    System.out.print(", Telefono: " + obInp.getTelefono()+"\n");
  }

  objIn.close();
} catch(Exception e){}  

}

As you can see, the catch exception it's empty, so, when i use my teacher's code, it looks like it's working flawlessly, but, i put a println there, and it always prints it. Meaning that something's wrong, and i'm pretty sure that is the 

while(fileIn != null)

bacause Netbeans says that this expression is never null. So i'm guessing that the program doesn't know what to do after he reaches the end of the file... Any sugestions pals? Thanks in an advance!

Here is the exception:

java.io.EOFException 
  at java.io.ObjectInputStream$BlockDataInputStream.peekByte(ObjectInputStream.java:2‌​577) 
  at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1315) 
  at java.io.ObjectInputStream.readObject(ObjectInputStream.java:369) 
  at profegraba.Persistencia.main(Persistencia.java:81)

Upvotes: 1

Views: 4647

Answers (3)

Duncan Jones
Duncan Jones

Reputation: 69329

The while loop is completely incorrect

while (fileIn != null) {

If your input file exists, then fileIn will always be non-null. You should check if fileIn is null immediately after constructing it, however, in case the file path is wrong.

Without the while loop, you are then just reading one object from the stream. Whether this is correct or not, I don't know. However, one should generally know how many objects were written to the stream so that the corresponding number of objects can be read back.

(You could read until you get an EOFException, however I wouldn't personally condone that. I'd suggest you instead stored a container object with a number of sub-objects. An EOFException may be thrown for reasons other than because the last object has been read successfully. However, I appreciate you may be forced to code this way to complete your assignment).

Finally, you need to ensure your input streams are closed, even if an exception occurs. If you are using Java 7, the try-with-resources construct can make this easier.

Upvotes: 2

afsantos
afsantos

Reputation: 5208

That exception means that you reached the end of the file, but you still ask for more objects to be read. The program can't read any more, because it has reached the end of the file, so the exception is thrown.

As mentioned before, you should handle your resources more carefully.

You should catch the exception and handle it naturally.

ObjectInputStream objIn = null;
try {
    FileInputStream fileIn = new FileInputStream("Serializado.txt");
    if (fileIn == null) {
        throw new IOException("Can't find file.");
    }
    objIn= new ObjectInputStream(fileIn);

    while (true) {
        obInp= (NewAlumno) objIn.readObject();
        System.out.print("Nombre   :" + obInp);
        System.out.print(", Sexo: " + obInp.getSexo());
        System.out.print(", Direccion: "+ obInp.getDireccion());    
        System.out.print(", Promedio: " + obInp.getpromedioPoo());
        System.out.print(", Telefono: " + obInp.getTelefono()+"\n");
    }
} catch (EOFException e) {
    // Ignore or do whatever you wanted to signal the end of file.
} catch (Exception ex) {
    ex.printStrackTrace();
} finally {
    try {
        if (objIn != null) {
            objIn.close();
        }
    } catch (IOException closeException) {
        closeException.printStackTrace();
    }
}

Upvotes: 1

user207421
user207421

Reputation: 310859

ObjectInputStream.readObject() throws EOFException when the end of the stream is reached. Your loop should be of the form while (true) or for (;;) and it should contain a catch (EOFException exc) block which breaks out of the loop.

Testing while (fileIn != null) is entirely futile.

Upvotes: 2

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