File length question...

Question

I'm a java student, and I'm having problems. I have to take the information from a Vector, and write it to a disk file on the A drive. Then I have to be able to read the file back into the Vector for processing. I can't find any info on how to do that. I've seen 347 different ways to CREATE a file that isn't already there... but how do I set the length to be written, and then how do I read and transfer the data back into the Vector? Any help would be greatly appreciated!! I'm so frustrated that my wife is worried I'm going to break my hand from punching the monitor so hard...

Answer 1

I will continue my search for information, and maybe I'll find it. Maybe it
has something to do with using a Vector instead of an ArrayList or
something...Nope, a Vector will do just as fine as an ArrayList. You shouldn't be
afraid to write some toy code and play with it. Here's a bit I type in on
the fly:public abstract class Person implements Serializable {
   public abstract void speak();
public class Fred extends Person {
   public void speak() { System.out.println("Wilmaaaa!!!!");
public class Barny extends Person {
   public void speak() { System.out.println("Jeez Fred ...");
public class Dino extends Person {
   public void speak() { System.out.println("Arf! Arf! Arfarfarf!");
}The following class attempts to create a List (or Vector if you want),
sticks three persons in it and tries to write the entire thing to a file:public class Test {
   static public void main(String[] args) {
      ObjectOutputStream oos= null;
      List<Person> list= new ArrayList<Person();
      list.add(new Fred());
      list.add(new Barney());
      list.add(new Dino());
      try {
         FileOutputStream fos= new FileOutputStream("test.data");
         oos= new ObjectOutputStream(fos);
         oos.writeObject(list);
      catch (Exception e) { e.printStackTrace(); }
      finally {
         try { oos.close(); } catch (Exception e) { /* muffle */ }
      ObjectInputStream ois= null;
      try {
         FileInputStream fis= new FileInputStream("test,data")l
         ois= new ObjectInputStream(fis);
         list= (List<Person>)ois.readObject();
         for (Person p : list)
            p.speak();
      catch (Exception e) { e.printStackTrace(); }
      finally {
         try { ois.close(); } catch (Exception e) { /* muffle */ }
}This was all from the top of my head, so no warranty etc. ;-)
You should get this up and running in no time; then play with it for a
while and see if you can understand what's happening.
kind regards,
Jos