How do I tell if I am at the EOF when using a DataInputStream?

I am having a hard time finding out when I reach the end of my file.  The all variables is an array of 5 NAMEs.  When I call the the below method, it should read each name from the file and stop when there is no more data in the file or the end of the array.  The file is Unicode and is created by the read method in the NAME class.  If your wondering why my class names are UPPERCASS, its cause I started it a few days ago after finishing a COBOL assignment and my brain wasn't working right :)


void Open_actionPerformed(ActionEvent e)
  {
    FileDialog D = new FileDialog(this, "Open Name File");
    D.setModal(true);
    D.setVisible(true);
    if(D.getFile() == null) return; // No File Selected
    String fileName = D.getDirectory() + D.getFile();
   
    try{
      in = new DataInputStream(new FileInputStream(new File(fileName)));
      for(int i=0; i<all.length && in != null; i++)
         NAME.read(in, this);
      in.close();
      in = null;

    }catch(IOException err){
      new ERRDIALOG(this, err.getMessage());
    }
  }


// My Code from my NAME class.


import java.io.*;
import java.awt.*;

public class NAME
{

  static final int NAME_LEN = 30;
  protected String firstName;
  protected String lastName;

  public NAME(String firstname, String lastname)throws NAMEEXCPTION
  {
    setFirstName(firstname.trim());
    setLastName(lastname.trim());
  }


  public void write(DataOutputStream out) throws IOException
  {
    int Lfirst = NAME_LEN - firstName.length();
    int Llast = NAME_LEN - lastName.length();
    String name = firstName;
    for(int i=0; i<Lfirst; i++)
        name += " ";
    out.writeChars(name);
    String lname = lastName;
    for(int i=0; i<Llast; i++)
        lname += " ";
    out.writeChars(lname);

  }

  static NAME read(DataInputStream in, Frame frame)
  {
    String FName = "";
    String LName = "";

    try{

      for(int i=0; i<NAME_LEN; i++)
        FName += in.readChar();

      for(int i=0; i<NAME_LEN; i++)
        LName += in.readChar();

      return new NAME(FName.trim(), LName.trim());

    }catch(IOException err){
      new ERRDIALOG(frame, err.getMessage());
    }catch(NAMEEXCPTION err){
      new ERRDIALOG(frame, err.getMessage());
    }
    System.out.println("Returning Null");
    return null; //should never reach this point.
  }

  void setFirstName(String name) throws NAMEEXCPTION
  {
    if(name == null || name.length() == 0)
      throw new NAMEEXCPTION("Name Format Error: Name cannot be: blank");
    else
      firstName = name;
  }

  void setLastName(String name) throws NAMEEXCPTION
  {
    if (name == null || name.length() == 0)
      throw new NAMEEXCPTION("Name Format Error: Name cannot be: blank");
    else
      lastName = name;
  }

  public String getFirstName(){return firstName;}
  public String getLasntName(){return lastName;}

  public String toString( )
  {
    return firstName+", " +lastName;
  }


  public static void main(String[] args)
  {
    try{
      NAME name = new NAME("Dan", "Demers");
      Frame f = new Frame("Frame Name");
      FileDialog D = new FileDialog(f, f.getTitle());
      D.setVisible(true);
      D.setModal(true);
      String file = D.getDirectory() + D.getFile();
      DataOutputStream out = new DataOutputStream(new FileOutputStream(file));
      name.write(f, out);out.flush();
      out.close();
      DataInputStream in = new DataInputStream(new FileInputStream(file));
      NAME N = name.read(in, f);
      in.close();
      System.out.println(N);

    }catch(Exception err){
      err.printStackTrace();
    }
    System.exit(0);
  }

}