Data I/O

• The primitive types, like int, could be represented in different ways on different machines. This is a problem.
• DataInput and DataOutput write data in a platform-independent form.
• Strings can be written in Unicode Text Format using writeUTF.

import java.io.*;
class DataInputOutputExample
{
  
  static BufferedReader system_in = new BufferedReader
    (new InputStreamReader(System.in));
  
  public static void main(String argv[])
  {

    // Create it
    {
      try
      {
        FileOutputStream fos = new FileOutputStream("data.dat");
        DataOutputStream dos = new DataOutputStream(fos);
        // Read in three hotels
        for (int i = 0; i < 3; i++)
        {
          Hotel a_hotel = new Hotel();
          a_hotel.input(system_in);
          a_hotel.write_to_dos(dos);
        }
        dos.close();
      }
      catch(IOException e)
      {
        System.err.println(e);
      }
    }

    // Now read it
    {
      try
      {
        FileInputStream fis = new FileInputStream("data.dat");
        DataInputStream dis = new DataInputStream(fis);
        Hotel a_hotel = new Hotel();
        while (a_hotel.read_from_dis(dis))
        {
          a_hotel.debug_print();
        }
        dis.close();
      }
      catch(IOException e)
      {
        System.err.println(e);
      }
    }

  }
}

class Hotel
{
  private String name;
  private int rooms;
  private String location;
  boolean input(BufferedReader in)
  {
    try 
    {
      System.out.println("Name: ");
      name = in.readLine();
      System.out.println("Rooms: ");
      String temp = in.readLine();
      rooms = to_int(temp);
      System.out.println("Location: ");
      location = in.readLine();
    }
    catch(IOException e)
    {
      System.err.println(e);
      return false;
    }
    return true;
  }
  boolean write_to_dos(DataOutputStream dos)
  {
    try
    {
      dos.writeUTF(name);
      dos.writeInt(rooms);
      dos.writeUTF(location);
    }
    catch(IOException e)
    {
      System.err.println(e);
      return false;
    }
    return true;
  }
  boolean read_from_dis(DataInputStream dis)
  {
    try
    {
      name = dis.readUTF();
      rooms = dis.readInt();
      location = dis.readUTF();
    }
    catch(EOFException e)
    {
      return false;
    }
    catch(IOException e)
    {
      System.err.println(e);
      return false;
    }
    return true;
  }
  void debug_print()
  {
    System.out.println("Name :" + name +
                       ": Rooms : " + rooms + ": at :" + location+ ":");
  }
  static int to_int(String value)
  {
    int i = 0;
    try
    {
      i = Integer.parseInt(value);
    }
    catch(NumberFormatException e)
    {}
    return i;
  }

}