Serializable ArrayList -- IOException error

Question

The code below returns an IOException. Here's my main:

public class Main 
{

    public static void main(String[] args) {

 Book b1 = new Book(100, "The Big Book of Top Gear 2010", "Top Gear",
                "BBC Books", 120, "Book about cars.");

 Book b2 = new Book(200, "The Da Vinci Code", "Dan Brown", "Vatican", 450,
                "A fast paced thriller with riddles.");

 Book b3 = new Book(300, "Le Petit Nicolas", "Sempe Goscinny", "Folio", 156,
                "The adventures of petit Nicolas.");

 ArrayList<Book> biblia = new ArrayList<Book>();

 biblia.add(b1);

 biblia.add(b2);

 biblia.add(b3);

 File f = new File("objects");

        try {

            FileInputStream fis = new FileInputStream("objects");

            int u = fis.read();

            if (u != -1) {

                ObjectInputStream ois = new ObjectInputStream(fis);

                Bookstore b = (Bookstore) ois.readObject();

                ois.close();

            } else {

                Bookstore b = new Bookstore(biblia);

                FileOutputStream fos = new FileOutputStream("objects");

                ObjectOutputStream oos = new ObjectOutputStream(fos);

                oos.writeObject(b);

                oos.close();

            }

        } catch (FileNotFoundException ex1) {

            System.out.println("File not found.");

        } catch (IOException ex2) {

            System.out.println("IO Error.");

        } catch (ClassNotFoundException ex3) {

            System.out.println("Class not found.");

        }

}

This is the Bookstore class which I use just to store the ArrayList of Book objects in orded to use it in Object streams.

public class Bookstore implements Serializable {


    private ArrayList<Book> myBooks = new ArrayList<Book>();

    public Bookstore(ArrayList<Book> biblia) {

        myBooks = biblia;

    } 

}

I've imported all the right libraries too. What I try to do is: If the file is not empty, then read the ArrayList from there (the bookstore object that contains the arraylist). If it's empty write a new one. The problem is that the only thing I get in returns is "IO Error." and I can't understand why.

You should think more about how to test if a file exists or not :). The way you are doing it now isn't really working. — Mihai Toader
– Mihai Toader, Commented Jan 20, 2011 at 1:30
inside of your catch(IOException ex2) block, add "ex2.printStackTrace();" to get the details of where your exception is occurring. — robert_x44
– robert_x44, Commented Jan 20, 2011 at 1:31
Thank you guys. It seems to work now, though I didn't change anything. :S — Felice
– Felice, Commented Jan 20, 2011 at 11:59

Robert Balent · Accepted Answer · 2011-01-20 01:48:30Z

2

It's wrong way to test if file exists. You are trying create stream from file which doesn't exists, and FileNotFoundException is thrown. Instead of:

FileInputStream fis = new FileInputStream("objects");            
int u = fis.read();
if (u != -1) {

just use

if(f.exists()) { ... }

edited Jan 20, 2011 at 1:48

answered Jan 20, 2011 at 1:35

Robert Balent

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1 Comment

Felice Over a year ago

I had already tried if(f.exists()) { ... } Nightsorrow and I thought fis.read() was an alternative but you are right it doesn't work right.

LINEMAN78 · Accepted Answer · 2011-01-20 01:31:19Z

1

It would help you debug these problems if you printed the stack trace when you get an exception, but I am guessing that Book is not serializable.

answered Jan 20, 2011 at 1:31

LINEMAN78

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Comments

Aaron Brown · Accepted Answer · 2011-01-20 01:45:37Z

1

Nightsorrow is probably right. To answer why you are getting "IO Error" out, it is because you told the program to print that if there was an IO Error. For the purposes of debugging your code I would delete the

catch (IOException ex2) {

        System.out.println("IO Error.");

    }

section of your code or comment it out so that you can get the stack trace. Then you can pinpoint where and why the error is occuring because it will give you an exception and what line that exception was thrown.

answered Jan 20, 2011 at 1:45

Aaron Brown

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