Dice Generator Probability

[Prince Pwn]

This application looks to be coded properly, but every time I run it, 1-4 "random" dice values are never landed on. Is this a bug with random and how long it takes to start at a new seed, or what?

Java:

/***********************************     Program:    Question 7.17     Date:       February 9, 2010 ***********************************/ import java.util.Random; public class Q717 {     public static void main (String[] args)     {         int die[] = new int [2];            // Two die to roll         int total = 0;                      // Stores addition of dice         int probability[] = new int [12];   // Number of possibilities         int amount = 36000;         Random dice;                        // Random dice generator         for (int i = 0 ; i < probability.length ; i++)  // For each possibility             probability [i] = 0;                        // Sets counter to 0         for (int i = 0 ; i < amount ; i++)   // Counts 36,000 times         {             dice = new Random ();             die [0] = 1 + dice.nextInt (6);  // New random instance             die [1] = 1 + dice.nextInt (6);  // New random instance             total = die [0] + die [1];       // Add the results             probability [total - 1] += 1;    // Increases counter on probability         }         // Graphical output         System.out.println ("Value\t|\tChances of Rolling Value ( /" + amount + " )");         System.out.println ("---------------------------------------------------");         for (int i = 1 ; i < probability.length ; i++)             System.out.println ((i + 1) + "\t|\t" + probability [i - 1]);     } }

[DemonWasp]

You're creating a new instance of Random every iteration through the loop, which probably has something to do with it. Either initialize and use a single Random object for all rolls, or, if you need a new one each time for some reason, use SecureRandom() which gives cryptographically secure "true" random numbers.

[Prince Pwn]

Thanks again, DemonWasp. Here's my final code:

Java:

/***********************************     Program:    Question 7.17     Date:       February 9, 2010 ***********************************/ import java.util.Random; public class Q717 {     public static void main (String[] args)     {         int die[] = new int [2];            // Two die to roll         int total = 0;                      // Stores addition of dice         int probability[] = new int [12];   // Number of possibilities         int amount = 36000;         Random dice;                        // Random dice generator         for (int i = 0 ; i < probability.length ; i++)  // For each possibility             probability [i] = 0;                        // Sets counter to 0         dice = new Random ();         for (int i = 0 ; i < amount ; i++)   // Counts X times         {             die [0] = 1 + dice.nextInt (6);  // New random instance             die [1] = 1 + dice.nextInt (6);  // New random instance             total = die [0] + die [1];       // Add the results             probability [total - 2] += 1;    // Increases counter on probability         }         // Graphical output         System.out.println ("Value\t|\tChances of Rolling Value ( /" + amount + " )");         System.out.println ("---------------------------------------------------");         for (int i = 1 ; i < probability.length ; i++)             System.out.println ((i + 1) + "\t|\t" + probability [i - 1]);     } }