/* An instance of this class represents a coin that can be tossed,
** (randomly) resulting in either HEADS or TAILS.
** It augments the capability of its predecessor class (TossableCoin3)
** in that a coin "remembers" its entire history of tosses.
*/
public class TossableCoin4 {

    // class constants
    // ---------------

    private static char HEADS = 'H';
    private static char TAILS = 'T';


   // instance variables
   // ------------------

   private boolean headsShowing; // true if HEADS, false if TAILS
   private int headsCntr;        // # times Heads was tossed
   private int tailsCntr;        // # times Tails was tossed
   private double headsProb;     // probability of Heads resulting from a toss
   private String tossHistory;   // String of H's and T's recording the results
                                 // of all past tosses of this coin


   /* Initializes this tossable coin to be "showing" HEADS and for the
   ** given number to be the probability of a toss resulting in Heads.
   ** pre: 0 <= hProb <= 1.0
   */
   public TossableCoin4(double hProb) {
      headsShowing = true; 
      headsCntr = 0;  // not necessary, as zero is the default value
      tailsCntr = 0;  // "
      headsProb = hProb;
      tossHistory = "";
   }

   /* Initializes this tossable coin to be a fair one initially
   ** "showing" HEADS. 
   */
   public TossableCoin4() { this(0.5); }


   // observers
   // ---------

   /* Reports whether this coin is showing HEADS.
   */
   public boolean isHeads() { return headsShowing; }

   /* Reports whether the k-th toss of this coin resulted in HEADS.
   */
   public boolean wasHeads(int k) { 
      return tossHistory.charAt(k-1) == HEADS;
   }

   /* Reports whether this coin is showing TAILS.
   */
   public boolean isTails() { return !headsShowing; }

   /* Reports whether the k-th toss of this coin resulted in TAILS.
   */
   public boolean wasTails(int k) { 
      return tossHistory.charAt(k-1) == TAILS;
   }

   /* Returns the number of times this coin has been tossed,
   ** with Heads being the result.
   */
   public int headsCount() { return headsCntr; }

   /* Returns the number of times this coin has been tossed,
   ** with Tails being the result.
   */
   public int tailsCount() { return tailsCntr; }

   /* Returns the number of times this coin has been tossed.
   */
   public int tossCount() { return headsCount() + tailsCount(); }


   /* Returns a string indicating which of the two faces
   ** is "showing".
   */
   public String toString() {
      String result;
      if (isHeads()) 
         { result = "HEADS"; }
      else 
         { result = "TAILS"; }
      return result;
   }


   // mutators
   // --------

   /* Tosses this coin.
   */
   public void toss() {
      headsShowing = Math.random() < headsProb;  //Notice the change from 0.5
      if (headsShowing) { 
         headsCntr = headsCntr + 1;
         tossHistory = tossHistory + HEADS;
      }
      else { 
         tailsCntr = tailsCntr + 1;
         tossHistory = tossHistory + TAILS;
      }
   }

}