InputStream object closes after declaration

Question

The code reads and writes objects with the help of XStream .

In the block of reading objects from the XML file in , the InputStream object is closed after declaration. That leads to an exception java.io.IOException: Stream Closed on the line

ObjectInputStream objectIn = stream.createObjectInputStream(in)

when compiling.

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

import com.thoughtworks.xstream.XStream;
import com.thoughtworks.xstream.io.xml.DomDriver;

public class PlayersXStreamIO
{
    public static void main(String... args) throws IOException, ClassNotFoundException
    {
        XStream stream = new XStream(new DomDriver());
        stream.setMode(XStream.ID_REFERENCES);

        if(args.length == 1)
        {
            try(OutputStream out = new FileOutputStream(args[0]);
                    ObjectOutputStream objectOut = stream.createObjectOutputStream(out))
            {
                Player max = new Player("max");
                max.setScore(5);
                Player moritz = new Player("moritz");
                moritz.setScore(3);
                objectOut.writeObject(max);
                objectOut.writeObject(moritz);
            }
        }
        else
        {
            try(InputStream in = new FileInputStream(args[0]);
                    ObjectInputStream objectIn = stream.createObjectInputStream(in))
            { // in.closed = true;
                List<Player> players = new ArrayList<>();
                while(in.available() > 0)
                {
                    players.add((Player) objectIn.readObject());
                }
                System.out.println(Arrays.toString(players.toArray()));
            }
        }
    }
}

The stack trace is:

 Exception in thread "main" java.io.IOException: Stream Closed at java.io.FileInputStream.available(Native Method) at capitel02.PlayersXStreamIO.main(PlayersXStreamIO.java:39) 

Answer 1

I guess that while wrapping the FileInputStream for the creation of an ObjectInputStream , the implementation already parses the complete file and closes it. Therefore, you get an end-of-stream exception. The solution would be to not access the file input stream itself, but only the created ObjectInputStream as referenced by the objectIn variable.

Answer 2

As proposed by Arie the problem is due to

while(in.available() > 0)

the readObject() should be used :

try{  

   List<Player> players = new ArrayList<>();
   while(trye){  
   {
         players.add((Player) objectIn.readObject());
   }  
} catch (EOFException e){};