;Ορισμός κλάσης Flat

public class Flat	{
    private double cost;
    private boolean sold = false;
    private double area;
    private int buildingNo;
    private int flatNo;
    static int totalFlats = 0;
    static Flat [] flats = new Flat[100];

    public Flat(double cost, double area, int buildingNo) {
       this.cost=cost;
       this.area=area;
       this.buildingNo = buildingNo;
       this.flatNo=totalFlats+1;
       totalFlats++;}

    public void setSold (boolean sold) {
      this.sold = sold;}

    public double calcPrice()   {
      return cost * area;}

    public void flatInfo () {
        System.out.println ("Building Number: " + buildingNo + 
			    " Flat Number: " + flatNo  + " Area: " 
                            + area + " Price: " + calcPrice () );}
 }


;Ορισμός κλάσης Apartment

public class Apartment extends Flat {
    private int numOfBeds;

    public Apartment (double cost, double area, int buildingNo, int numOfBeds) {
       super(cost, area, buildingNo);
       this.numOfBeds = numOfBeds;}

    public void flatInfo () {
       super.flatInfo() + System.out.println (" Number of bedrooms: " + numOfBeds);}
}


;Ορισμός κλάσης Studio

public class Studio extends Flat {
    private double extraCost;
    private boolean furnished;

    public Studio (double cost, double area, int buildingNo) {
       super(cost, area, buildingNo);
       this.extraCost = 0;
       this.furnished = false;}

    public Studio (double cost, double area, int buildingNo, double extraCost) {
       super(cost, area, buildingNo);
       this.extraCost = extraCost;
       this.furnished = true;}

    public double calcPrice () { 
       return super.calcPrice() + extraCost;}

    public void printInfo() {
      if furnished super.flatInfo() + System.out.println("Furnished: " + "yes");
      else super.flatInfo() + System.out.println("Furnished: " + "no");}
}


;Ορισμός κλάσης Building

public class Building {
   private int buildingNo;
   private String street;
   private String city;
   private int buildingTotalFlats = 0;
   private Flat [] flats = new Flat[10];
   static Building [] buildings = new Building[10];
   static int totalBuildings = 0;
    
   public Building(String street, String city)	{    
    	this.street=street; 
    	this.city=city;
        this.BuildingNo = totalBuildings + 1;
        totalBuildings++;}
    }

    public void setFlat(Flat f){
        this.flats[buildingTotalFlats+1] = f;
        this.buildingTotalFlats++;}

    public void buildingInfo () {
        System.out.println("Street: " + street +", City: " + city + 
                           ", Number of flats: " + buildingTotalFlats);
        for(int i=0;i<buildingTotalFlats;i++)
           {
        	System.out.println(flats[i].flatInfo());
           }
    }}