import java.util.Random;

/** An instance of this class models a coin that can be tossed to yield 
**  heads or tails, with equal probability.
**
**  @author R. McCloskey
**  @version August 2008
*/

public class TossableFairCoin {

   /*    d a t a    */

   private boolean headsUp;  // true means heads is showing, false means tails
   private Random ran;       // for tossing the coin
   private int headsCntr;    // # of heads tossed in lifetime of coin
   private int tailsCntr;    // # of tails tossed in lifetime of coin

   private static final String HEADS_STR = new String("Heads");
   private static final String TAILS_STR = new String("Tails");


   /*   c o n s t r u c t o r   */

   /** Initializes the coin's fields.
   */
   public TossableFairCoin() {
      headsCntr = 0;
      tailsCntr = 0;
      ran = new Random();
   }


   /*   o b s e r v e r s  */

   /** Reports whether or not the coin is showing heads.
   **  @return true if the coin is showing heads, false otherwise
   */
   public boolean isHeads() { return headsUp; }

   /** Reports whether or not the coin is showing tails.
   **  @return true if the coin is showing tails, false otherwise
   */
   public boolean isTails() { return !isHeads(); }


   /** Reports the number of times during its lifetime that the coin
   **  has been tossed to yield heads.
   **  @return number of times the coin has been tossed to yield heads
   */
   public int numHeadsTossed() { return headsCntr; }


   /** Reports the number of times during its lifetime that the coin
   **  has been tossed to yield tails.
   **  @return number of times the coin has been tossed to yield tails
   */
   public int numTailsTossed() { return tailsCntr; }


   /** Reports the number of times during its lifetime that the coin
   **  has been tossed.
   **  @return number of times the coin has been tossed 
   */
   public int numTimesTossed() { return headsCntr + tailsCntr; }


   /** Returns a string indicating which side of the coin is showing,
   **  heads or tails.
   **  @return a string indicating which side of the coin is showing
   */
   public String toString() {
      return isHeads() ?  HEADS_STR : TAILS_STR;

      /* the above is equivalent to the following if statement: */
      // if (isHeads())
      //   { return HEADS_STR; }
      // else
      //   { return TAILS_STR; }
   }


   /*   m u t a t o r   */

   /** Tosses the coin, after which there is a probability of 1/2 that
   **  the coin shows heads, and similarly for tails.
   */
   public void toss() { 
      headsUp = ran.nextBoolean();
      if (isHeads()) 
         { headsCntr++; }
      else 
         { tailsCntr++; }
   }


}