Help with simple project..?

[minakrn]

Hi ^^,

I am new programmer that need help with this idea. I am trying to write a simple simulation for the process of rolling two n-sided dice and recording the sum of the outcomes. However, the sum of the outcomes are duplicated. How can I get rid of this?

Here is my program:

// import necessary package
import java.util.*;

// declare class
class TwoRolls {

  public static void main (String args[]) 
  {
	  
	// print introduction message
	System.out.println("\n\n\t\t\t\t\t=== RANDOM TWO ROLL IMPLEMENTATION PROGRAM ===   \n");
	
	// declare and initialize local variables
	int entry;
	int double_entry; 
	
	int counter_1 = 0;
	int counter_2 = 0;
	
	// declare local array
	int sum[];
	
	// prompt user for input
	System.out.print( "Enter your desirable positive n-value: " );
    
	    // declare scanner object
        Scanner input = new Scanner( System.in);
        
        // read input with scanner object
        entry = input.nextInt();

        // conditional exception when input is a negative n-value
      	if (entry <= 0)
		{	
			System.out.println( "\nThat is an invalid entry. ");
		    System.out.print("\nTERMINATING PROGRAM");
			
		}
		
      	// conditional exception when input is a positive n-value
		else
		{
			System.out.println("\nYour new n-value entry: " + entry);
			
			// initialize variable by multiplying input by two
			double_entry = entry * 2;
		
			// call reference to proper method
			sum = randomRoll(entry);
			
			System.out.print("\n\n[SUM]\t\t\t[APPEARANCE]");
			System.out.println("\n------------------------------------------------//");
			
			// outer loop statement that increments counter to read the overall array 
			for (int counter = 0; counter < sum.length; counter++)
			{	
				// re-initialize variable
				counter_2 = 0;
				
				// inner loop statement that increments counter to check for similar values
				for(counter_1 = 0; counter_1 < sum.length; counter_1++)
				{
					// conditional exception when similar value is found
					if (sum[counter] == sum[counter_1])
					{
						// increment counter	
						counter_2++;
					}
					
				}
				
				// print output according to format
				System.out.println(sum[counter] + "\t\t\t" + counter_2);
				
			}
										
		}
			
  } // terminate main function

  
  // method call to randomRoll
  public static int[] randomRoll(int n_value)
  {
	  // declare local variables
	  int first_roll;
	  int second_roll;
	  
	  // declare and initialize local array in terms of number of attempts
	  int[] sum_array = new int[10];
	  
	  
	    // loop statement that increments counter in accordance to the number of attempts
		for (int counter = 0; counter < sum_array.length; counter++)
		{
			// mark each roll variable to a random value according to specification 
			first_roll = 1 + (int)(Math.random() * n_value);
			second_roll = 1 + (int)(Math.random() * n_value); 
	
			// mark the sum
			sum_array[counter] = first_roll + second_roll;
		
			// print informational output in regards to each roll and total sum
			System.out.println("\n\t\t\tFIRST ROLL  = " + first_roll);
			System.out.println("\t\t\tSECOND ROLL = " + second_roll);
		
			System.out.println("\n\t\t\t\t\t\tTOTAL SUM = " + sum_array[counter]);
		
		}
		
		// recall result back to the main function
		return sum_array;
		
  	} // terminate randomRoll method
  
} // terminate TwoRolls class

Hope anyone can help me ^^. Thank you~

[Nathandelane]

Okay great problem - here's what I would change, and it should be fairly simple - instead of using Math.random(), use java.util.Random with a seed. You can create a seed by getting the current datetime from java.util.Calendar like this: long seed = java.util.Calendar.getInstance().getTimeInMillis() ; Then plug that seed into the constructor for a new Random object. So basically instead of:

first_roll = 1 + (int)(Math.random() * n_value);
second_roll = 1 + (int)(Math.random() * n_value);

do:

long seed = java.util.Calendar.getInstance().getTimeInMillis() ;
Random r = new java.util.Random(seed);

first_roll = 1 + (int)(r.nextInt() * n_value);
second_roll = 1 + (int)(r.nextInt() * n_value);

Does that help you out? Does that work?

Nathan