CSci 101: Homework 2

Objectives

In this programming assignment you will design, write and test a computer program with branching statements and loops. The problem description is given below. If you would like a more challenging program, see the one at the end of this assignment.

Problem

Write a Java program that simulates flipping coins and counts the coin flips. The program should ask the user how many times to flip the coin, then simulate flipping the coin that many times (using a random number generator), prints a symbol (H or T) for each coin flip, and provides a summary giving the total number of heads and tails.

Discussion

As always, your program should first output an introductory message to the user explaining what the program does. Then prompt the user to enter the number of coins to flip. The program will need a loop, and the instructions inside the loop should deal with flipping the coin once. You can simulate the coin flip with a random number generator. One way to do that in Java is to use the Math.random method. When you need to simulate a coin flip, you call the Math.random method to generate a random number x between 0 and 1 (greater than or equal to 0, but strictly less than 1). This random number has a uniform distribution, so the probability that it's less than 0.5 is one half. Thus, the condition 
          if (Math.random() < 0.5)
can be used to decide when the coin is flipped heads. If it is heads, print an H and increase the counter for the number of heads. Otherwise, print T and increase the tail counter.

Sample Execution

  This program will simulate flipping a fair coin.

  How many times would you like the coin to be flipped? 50

  Here is the sequence of coin flips:

  THHTHTHHTTTHTHTTTTHHTHTHTHHTHTHHTHTHHTTHTTTHHHTHTT

  There were 24 heads and 26 tails.

Testing

Run your program several times. You should get different results each time.

Deliverables

Turn in the following items:
  1. A printout of your program on paper
  2. A printout showing the 2 runs of your program with 100 coinflips each.

Grading will be as for the last homework assignment.

Challenge program

If you prefer, you can try this challenge program instead of the one above. Change from flipping a coin to tossing a pair of dice. Keep track of the sum of the dice, and print the output in a histogram. Use a * for each time a sum occurs, so if there are eight 7's, then after 7 print out ********. Here's what a sample run might look like: 
  This program will simulate tossing a pair of dice.

  How many times would you like the dice to be tossed?  20

  Here is the sequence of sums, one for each toss:

  8 6 3 9 6 7 2 11 5 8 4 7 9 9 6 10 7 5 11 7

   2: *
   3: *
   4: *
   5: **
   6: ***
   7: ****
   8: **
   9: **
  10: *
  11: **
  12: