Writing an ArrayList of non-string objects to file

Question

EDIT: I solved the problem, I forgot to close the ObjectOutputStream. 'doh! I'll leave the question just in case someone wants to propose a more elegant option, which would be much appreciated.

I currently am trying to write a class called phonebook to file, which contains an ArrayList of objects called PhonebookEntry. Here is the Phonebook class:

import java.util.ArrayList;
import java.io.*;

public class Phonebook implements Serializable
    private static final long serialVersionUID = 1;

    ArrayList<PhonebookEntry> phonebookEntries = new ArrayList<PhonebookEntry>();

    public void addEntry(String name, String number) {
        PhonebookEntry newEntry = new PhonebookEntry(name, number);
        phonebookEntries.add(newEntry);
    }

}

I have tried using a simple ObjectInput/OutputStream and I can get it to save that way, but not to load (usually with an EOFExcpetion). Is there an elegant way to save an object like this, or is there any way to save an ArrayList of objects to a file?

How are you trying to load it again after saving it using an `ObjectOutputStream`? — Jesper, Dec 07 '11 at 14:43
I get an EOFException error when I try to load it using ois.readObject(); (ObjectInputStream) — Elianora, Dec 07 '11 at 15:07
Can you post the code you're using to read/write via the ObjectOutputStream? — Reverend Gonzo, Dec 07 '11 at 15:13
In production code you may not want to use `serialVersionUID = 1`. Rather let you IDE generate an appropriate ID for you. — DerMike, Dec 07 '11 at 15:15

score 0 · Accepted Answer · answered Dec 07 '11 at 15:21

The following works. I'm guessing you're missing flush() or close().

public static void main(final String[] args) throws IOException, ClassNotFoundException {
    final ObjectOutputStream out = new ObjectOutputStream(new FileOutputStream("test.out"));
    final Phonebook phonebook = new Phonebook();
    out.writeObject(phonebook);
    out.flush();
    out.close();

    final ObjectInputStream in = new ObjectInputStream(new FileInputStream("test.out"));
    final Object o = in.readObject();
    System.out.println(o);
}

score 0 · Answer 2 · answered Dec 07 '11 at 15:24

0

When you want your PhonebookEntries to be serialized the standard way, its members must be serializable itself.

answered Dec 07 '11 at 15:24

DerMike

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score -1 · Answer 3 · answered Dec 07 '11 at 14:53

-1

A couple of different issues, the code as written, which I'm assuming is a sample code (so I'm not going to fix it) is never going to fill in anything since you keep releasing the object. So you would end up with null,null for each add.

To answer your question, not sure how much more eligent it is but the shorter version is:

for (PhonebookEntry pbe : phonebookEntries) {
    System.out.println("Name: " + pbe.getName());
    ....
}

answered Dec 07 '11 at 14:53

awm

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I'm not sure I understand awm's answer... it has nothing to do with file io, but maybe I'm missing something... I'm trying to save the entire Phonebook object into a file with all of the PhonebookEntry objects inside it. – Elianora Dec 07 '11 at 15:05

Writing an ArrayList of non-string objects to file

3 Answers3

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