Java Practice int SIDES = 6; double [] dist = new double[2*SIDES+1]; for (int i

Question

Java Practice

int SIDES = 6;
double [] dist = new double[2*SIDES+1];
for (int i = 1; i<= SIDES; i++)
for(int j = 1; j <= SIDES; j++)
dist[i+j] += 1.0;

for (int k = 2; k <= 2*SIDES; k++)
dist[k] /= 36.0;

The value dist[k] is the probability that the dice sum to k. Run experiments to validate this calculation simulating N dice throws, keeping track of the frequencies of occurrence of each value when you compute the sum of two random integers between 1 and 6. How large does N have to be before your empirical results match the exact results to three decimal places?

Write a java program  

named "DiceSimulation.java"  

which conducts a modified version of the experiment above

modification is doing 4 decimal places instead of 3

printing out only one value of N.

Explanation / Answer

import java.text.DecimalFormat;
import java.util.Random;
public class DiceSimulation
{
private static int SIDES = 6;
private static double [] dist;
public static void main(String[] args)
{
sumDiceProb();
simulation(10000000);
}
public static void sumDiceProb()
{
int n = 2*SIDES;
dist = new double[n+1];
for (int i=1; i<=SIDES; i++)
{
for (int j=1; j<=SIDES; j++)
{
dist[i+j] += 1.0;
}
}
DecimalFormat df = new DecimalFormat("#.###");
double total = 0.0;
System.out.println("original probabilities: ");
for (int i=2; i<=n; i++)
{
dist[i] /= 36.0;
total += dist[i];
System.out.print(df.format(dist[i]) + " ");
}
System.out.println();
//System.out.println("total: " + total);
}
public static void simulation(int n)
{
int m = 2*SIDES;
double [] freq = new double[m+1];
Random rand = new Random();
for (int i=1; i<=n ;i++)
{
int v1 = rand.nextInt(6) + 1;
int v2 = rand.nextInt(6) + 1;
++freq[v1+v2];
}
System.out.println("after running simulation for " + n + " trials - probablities are: ");
DecimalFormat df = new DecimalFormat("#.###");
for (int i=2; i<=m; i++) {
freq[i] /= n;
System.out.print(df.format(freq[i]) + " ");
}
}
}

Related Questions

Navigate

• Browse (All)
• Browse J
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.