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

public class OpenFileDemo
{
   public static void main(String[] args)
   {
      try
      {
         ObjectOutputStream outputStream = openFile();
         int n;

         System.out.println("Enter nonnegative integers.");
         System.out.println("Place a negative number at the end.");
         Scanner keyboard = new Scanner(System.in);

         do
         {
            n = keyboard.nextInt();
            outputStream.writeInt(n);
         }while (n >= 0);

         System.out.println("Numbers and sentinel value");
         System.out.println("written to the file.");
         outputStream.close();
      }
      catch(IOException e)
      {
         System.out.println("Problem with output to file.");
      }
   }


   public static ObjectOutputStream openFile( ) throws IOException
   {
       ObjectOutputStream tempStreamName;
       System.out.println("Enter file name:");
       Scanner keyboard = new Scanner(System.in);
       String fileName = keyboard.next( );
       tempStreamName =
          new ObjectOutputStream(new FileOutputStream(fileName));
       return tempStreamName;
    }

}