The problem is not with FileOutputStreams but with
ObjectOutputStream(f). ObjectOutputStream is the consistent database and
it must be written and read entirely 'in one eat'. This does not mean
you cannot save two ObjectStreams to one file, but it is up to you to
divide your file to the 2 relevant parts when reading it.
Try change your code to something like this:
public static void main(String argv[])
{
final int portion = 2;
int i;
try
{
FileInputStream
f = new FileInputStream("out");
ObjectInputStream o;
while (true)
{
i = portion;
o = new ObjectInputStream(f);
while(i-- > 0) System.err.println("Saw: " + (String)o.readObject());
}
}
catch (Exception e)
{
System.err.println(e.toString());
}
}
Or you can store the number of object before objects if it is more
relevant for your application.
Hope this helps
Pavel
> public static void main(String argv[])
> {
> try
> {
> FileInputStream
> f = new FileInputStream("out");
>
> ObjectInputStream
> o = new ObjectInputStream(f);
>
> while (true)
> System.err.println("Saw: " + (String)o.readObject());
> }
> catch (Exception e)
> {
> System.err.println(e.toString());
> }
> }
int firstPortion = 2; //objects
FileInputStream
f = new FileInputStream("out");
ObjectInputStream
o = new ObjectInputStream(f);
while (true)
System.err.println("Saw: " + (String)o.readObject());
"Frank B. Brokken" wrote:
>
> Dear listmembers,
>
> I have a problem using FileOutputStreams. I want to be able to append to
> an existing file, and I would like to be able to read the information back
> later.
>
> To write to the file, I use the following small program, in which a
> FileOutputStream is opened in append-mode, followed by the writing of two
> Strings:
>
> ///////////////////////////////////////////////////////////
> import java.io.*;
>
> public class writer
> {
> public static void main(String argv[])
> {
> try
> {
> FileOutputStream
> f = new FileOutputStream("out", true); // open in append mode
>
> ObjectOutputStream
> o = new ObjectOutputStream(f);
>
> o.writeObject("hello"); // write 2 strings
> o.writeObject("world");
> o.flush();
> f.close();
> }
> catch (Exception e)
> {
> System.err.println(e.toString());
> }
> }
> }
> //////////////////////////////////////////////////////
>
> Then, to read the file again, I use the following small program:
>
> //////////////////////////////////////////////////////
> import java.io.*;
>
> public class reader
> {
> public static void main(String argv[])
> {
> try
> {
> FileInputStream
> f = new FileInputStream("out");
>
> ObjectInputStream
> o = new ObjectInputStream(f);
>
> while (true)
> System.err.println("Saw: " + (String)o.readObject());
> }
> catch (Exception e)
> {
> System.err.println(e.toString());
> }
> }
> }
> ////////////////////////////////////////////////////////////
>
> Now, after running writer the first time, 'out' is created, and contains
> (hex):
>
> 00000000: AC ED 00 05 74 00 05 68 65 6C 6C 6F 74 00 05 77 ....t..hellot..w
> 00000010: 6F 72 6C 64 orld
>
> The reader program reads this, and shows:
>
> Saw: hello
> Saw: world
> java.io.EOFException: Expecting code
>
> So far, so good. Now I run writer again, and this results in the following
> contents of the file 'out':
>
> 00000000: AC ED 00 05 74 00 05 68 65 6C 6C 6F 74 00 05 77 ....t..hellot..w
> 00000010: 6F 72 6C 64 AC ED 00 05 74 00 05 68 65 6C 6C 6F orld....t..hello
> 00000020: 74 00 05 77 6F 72 6C 64 t..world
>
> Note the byte at offset 0x14: it is 0xac, which is -84 when the byte is viewed
> as a signed 8 bits value. When I now run reader, it tells me:
>
> Saw: hello
> Saw: world
> java.io.StreamCorruptedException: Type code out of range, is -84
>
> What I make of this is that the initial bytes of the file (ac ed) are
> appended every time the writer program is started again. The first time I
> start writer the two strings are written consecutively, without any special
> bytes in between. So it looks as if the intermediate ac ed bytes shouldn't be
> there.
>
> So, I wonder if I'm doing something wrong here. If any of you guys could help
> me out (maybe by sending email directly to [EMAIL PROTECTED]), I'd be very
> grateful.
>
> Thanks in advance,
>
> --
> Frank B. Brokken (al sinds enige jaren uitgedost (untranslatable))
> My extended signature is at http://www.icce.rug.nl/frank/signature
>
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