Serialization question: can't write an object

Question

this may be a simple question but I do need to find out what's wrong with the object I am trying to serialize:
The method (included) I use to write object works fine for some simple objects but stops without giving any message for some complex objects. It stops at "out.writeObject(obj)". Is there any other exceptions need to be caught or something else. Thanks a lot.
public void writeAnObject(Object obj) {
ObjectOutputStream out = null;
try {
out = new ObjectOutputStream(new FileOutputStream("obj.saved"));
out.writeObject(obj);
out.close();
} catch (FileNotFoundException e) {
System.err.println("Caught FileNotFoundException");
e.printStackTrace(System.err);
} catch (IOException e) {
System.err.println("Caught IOException ");
e.printStackTrace(System.err);

Answer 1

Ok, one last thing... don't know if it will make any differance but why not?! This is a class that I used successfully in several projects when serializising Collections to file:
* @author Andrew
* @version 1.0 (2000-11-24)
public class PersistentStorage {
     // The objectoutputstream
     private ObjectOutputStream out;
     // The objectinputstream
     private ObjectInputStream in;
      * This method saves a collection persistent to specified file.
      * @param obj          The collection we want to save.
     public void saveCollection(Collection obj, String fileName)
          throws FileNotFoundException, IOException {
          // Create a objectoutputstream
          out = new ObjectOutputStream(new FileOutputStream(fileName));
          // Write the collection object to file
          out.writeObject(obj);
          // Close the objectoutputstream
          out.close();
      * This method read a collection object from specified file.
      * @return collection          The collection we have read.
     public Collection readCollection(String fileName)
          throws FileNotFoundException, IOException, ClassNotFoundException {
          // Create a objectinputstream
          in = new ObjectInputStream(new FileInputStream(fileName));
          // Asign the read object to a Collection "container"
          Collection collection = (Collection) in.readObject();
          // Close the objectinputstream
          in.close();
          return collection;
}The differens is that I don't catch any exceptions in those method writing and reading objects. Only throw exceptions.
Try it out and see if it helps... (last shot) ;)
/Andrew