/* The CD Collection example illustrating support methods
   (from Lewis & Loftus, first edition) */

import java.text.*;

class CD_Collection {

   private int num_cds;
   private double value_cds;

   public CD_Collection (int initial_num, double initial_value) {
     num_cds = initial_num;
     value_cds = initial_value;
   }

   public void add_cds (int number, double value) {
     num_cds = num_cds + number;
     value_cds = value_cds + value;
   }

   public void print () {

     // The output will have only 2 digits after the decimal point.
 
     DecimalFormat precisionTwo = new DecimalFormat ("#.00");

     System.out.println ("*****************");
     System.out.println ("Number of CDs: " + num_cds);
     System.out.println ("Value of collection: $" + 
                  precisionTwo.format(value_cds));
     System.out.println ("Avarage cost per CD: $" + 
                  precisionTwo.format(average_cost()));
   }

   private double average_cost () {
     return value_cds / num_cds;
   }
}

class Tunes {

   public static void main (String[] args) {
     CD_Collection music;
     music = new CD_Collection (5, 59);
     music.print ();
     music.add_cds (1, 10.99);
     music.add_cds (3, 39.34);
     music.add_cds (2, 24.73);
     music.print ();
     music.add_cds (2, 20.82);
     music.add_cds (4, 46.90);
     music.print ();
   }
}