public abstract class Space extends Object
public Space()
public abstract String getType()
public abstract double getSize()

public class Room  extends Space
public Room(String type,
           double area)
public String getType()
public double getSize()

public class Apartment extends Space
public static final String KITCHEN
public String getType()
public double getSize()
public Room[] getRooms()

public class ApartmentFileHandler extends Object implements Serializable {
 
   private OutputStream outStream;
   private ObjectOutputStream obStream; 
   private String filePath; 
 
 
       public ApartmentFileHandler(String filePath) {
          this.filePath = filePath;
       }
 
 
/** Writes the given apartment data in the file. If the file already 
exists, the old contents are overwritten.
Parameters:
apartment - the apartment to be written in the file
Throws:
IOException - if other problems arose when handling the file (e.g. the 
file could not be written)
*/
 
       public void write(Apartment apartment)
          throws IOException {
          
          outStream = new FileOutputStream(filePath);
          obStream = new ObjectOutputStream(outStream);
               
          obStream.writeObject(apartment);
 
       }
}

import java.io.*;
import java.util.*;
              
 
public class ApartmentWriterProgram 
extends Object
              
   private KeyboardReader keyboardReader; 
   private List roomsInList; 
   private Room[] rooms;
   private int numberOfRooms; 
   private String file; 
              
 
         public ApartmentWriterProgram()
 
           this.keyboardReader = new KeyboardReader();
           this.roomsInList = new ArrayList();
           this.rooms = new Room [numberOfRooms]; 
       }
              
 
/** Runs the writer program. The program asks the user for some 
apartment data and a file name, and saves the data in the file. */
 
         public void run() { 
           
           try {
        
             numberOfRooms = keyboardReader.getInt("Give number of rooms: ");
             for (int i =1; i<numberOfRooms+1; i++) {
                String type =keyboardReader.getString("Give " +i+ ". " + "type of the room: ");
                double area =keyboardReader.getDouble("Give " +i+ ". " + "area of room: ");
    
                Room room= new Room(type, area);
                this.roomsInList.add(room);
             }
             roomsInList.toArray(rooms); 
             Apartment apartment = new Apartment(rooms);
            
             System.out.println(); 
             file = keyboardReader.getString("Give name of the file: ");
        
             ApartmentFileHandler handler = new ApartmentFileHandler(file);
             handler.write(apartment); 
        
          } catch (IOException ioe) {
            System.out.println("Writing to file "+file+ " failed.");
          }
           
       }
              
        public static void main(String[]  args) {
             ApartmentWriterProgram program = new ApartmentWriterProgram();
             program.run(); 
       } 
                     
 
}