Page 421 - Introduction to Programming with Java: A Problem Solving Approach

10.6 Problem Solving with Array Case Studies 387
/*********************************************************************
*
CoinFlips.java
Dean & Dean
This generates a histogram of coin flips.
*********************************************************************/
*
*
*
public class CoinFlips
{
public static void main(String[] args)
{
final int NUM_OF_COINS = 3;
// number of coins
final int NUM_OF_REPS = 1000000; // repetitions
// The frequency array holds the number of times
// a particular number of heads occurred.
int[] frequency = new int[NUM_OF_COINS + 1];
int heads;
// heads in current group of flips
double fractionOfReps; // head count / repetitions
int numOfAsterisks;
// asterisks in one histogram bar
for (int rep=0; rep<NUM_OF_REPS; rep++)
}
// end class CoinFlips
}
// end main
{
}
// end for
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// perform a group of flips
heads = 0;
for (int i=0; i<NUM_OF_COINS; i++)
{
{
}
heads += (int) (Math.random() * 2);
}
frequency[heads]++;
// update appropriate bin
}
// end for
System.out.println(
"Number of times each head count occurred:");
for (heads=0; heads<=NUM_OF_COINS; heads++)
{
System.out.print(
" " + heads + " " + frequency[heads] + " ");
fractionOfReps = (float) frequency[heads] / NUM_OF_REPS;
numOfAsterisks = (int) Math.round(fractionOfReps * 100);
for (int i=0; i<numOfAsterisks; i++)
System.out.print("*");
System.out.println();
This loop fills up the frequency bins. Each iteration simulates one group of three coin flips.
This loop prints the histogram. Each iteration prints one histogram bar.
Figure 10.9 CoinFlips program that generates a histogram for coin-flips simulation