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Thread: Why is the output always "0"?

  1. #1
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    Default Why is the output always "0"?

    So I am trying to write a Java program that simulates a Powerball ticket.

    It uses the Random function to generation 5 numbers, followed by a special number within a different range.

    It uses arrays for everything.

    The first 5 numbers are randomized nicely, but the "Special Number" is always 0.
    Can someone please help me to figure out why?

    Thanks

    import java.util.Random;
     
    public class Test
    {
    	public static void main(String args[])
    	{
    		final int NUM_row = 4;
    		final int Num_columns=6;
    		int[][] numbers = new int[NUM_row][Num_columns];
    		Random randomNumbers = new Random();
    		int row, columns;
     
    		final int PowerNUM_row = 4;
    		final int PowerNum_columns=5;
    		int[][] Powernumbers = new int[PowerNUM_row][PowerNum_columns];
    		Random PowerrandomNumbers = new Random();
    		int Powerrow, Powercolumns=0 ;
     
    		for (Powerrow = 0; Powerrow < 3; Powerrow++)
    			for (Powercolumns = 0; Powercolumns < 1; Powercolumns++)
    				Powernumbers[Powerrow][Powercolumns] = PowerrandomNumbers.nextInt(12);
     
    		for (row = 0; row < 3; row++)
    			for (columns = 0; columns < 5; columns++)
    				numbers[row][columns] = randomNumbers.nextInt(49); 
     
    		System.out.printf("Power Ball Ticket: \n\n");
    		for (row = 0; row < 1; row++)
    		{
    			for (columns = 0; columns < 5; columns++)
    			{
    				System.out.printf("%d ",numbers[row][columns]);
    			}
    			System.out.printf("Power Ball: %d", Powernumbers[Powerrow][Powercolumns]);
    			System.out.println();
    		}
    	}
    }


  2. #2
    Super Moderator jps's Avatar
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    Default Re: Why is the output always "0"?

    import java.util.Random;
     
    public class Test
    {
    	public static void main(String args[])
    	{
    		final int NUM_row = 4;// Note NUM is all caps vs below....
    		final int Num_columns=6;// You should stick to one style, not NUM and Num
    		int[][] numbers = new int[NUM_row][Num_columns];
    		Random randomNumbers = new Random();
    		int row, columns;
     
    		final int PowerNUM_row = 4;
    		final int PowerNum_columns=5;
    		int[][] Powernumbers = new int[PowerNUM_row][PowerNum_columns];
    		Random PowerrandomNumbers = new Random();
    		int Powerrow, Powercolumns=0 ;
     
    		for (Powerrow = 0; Powerrow < 3; Powerrow++)// What is this 3 here?
    			for (Powercolumns = 0; Powercolumns < 1; Powercolumns++)//...and this 1?
    				Powernumbers[Powerrow][Powercolumns] = PowerrandomNumbers.nextInt(12);//..and this 12?
     
    		for (row = 0; row < 3; row++)//..and this 3>
    			for (columns = 0; columns < 5; columns++)//...and this 5>
    				numbers[row][columns] = randomNumbers.nextInt(49); //and this 49?
     
    		System.out.printf("Power Ball Ticket: \n\n");
    		for (row = 0; row < 1; row++)//...and this 1?
    		{
    			for (columns = 0; columns < 5; columns++) //...and this 5?
    			{
    				System.out.printf("%d ",numbers[row][columns]);
    			}
    			System.out.printf("Power Ball: %d", Powernumbers[Powerrow][Powercolumns]);
    			System.out.println();
    		}
    	}
    }
    My first suggestion is to clean up all of those magical numbers. Here is the reason why. As I look over your code to see what is going on, it is not easy to follow. To you, now since its fresh, it may be clear. But to someone else, and to you after you have done other things, this will be hard to read. Replace the magic numbers with variables of good names, and maybe the error will be easier to spot.

  3. #3
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    Default Re: Why is the output always "0"?

    Quote Originally Posted by TheBattousaixx View Post
    ...help me to figure out...
    Make the program tell you what it is writing to and reading from the Powernumbers array:
            for (Powerrow = 0; Powerrow < 3; Powerrow++)
            {
                for (Powercolumns = 0; Powercolumns < 1; Powercolumns++)
                {
                    Powernumbers[Powerrow][Powercolumns] = PowerrandomNumbers.nextInt(12);
     
                    // For debugging
                    System.out.printf("\n 1: Powernumbers[%d][%d] = %d\n",
                            Powerrow, Powercolumns, Powernumbers[Powerrow][Powercolumns]);
     
                }
            }
    .
    .
    .
            for (row = 0; row < 1; row++)
            {
                for (columns = 0; columns < 5; columns++)
                {
                    System.out.printf("%d ",numbers[row][columns]);
                }
     
                // For debugging
                System.out.printf("\n 2: Powernumbers[%d][%d] = %d\n",
                        Powerrow, Powercolumns, Powernumbers[Powerrow][Powercolumns]);
     
                System.out.printf("Power Ball: %d", Powernumbers[Powerrow][Powercolumns]);
                System.out.println();
            }


    Cheers!

    Z
    Last edited by Zaphod_b; July 24th, 2012 at 04:14 PM.

  4. #4
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    Default Re: Why is the output always "0"?

    public class Test
    {
    	public static void main(String args[])
    	{
    		final int NUM_row = 4;
    		final int Num_columns=6;
    		int[][] numbers = new int[NUM_row][Num_columns];
    		Random randomNumbers = new Random();
    		int row, columns;
     
    		final int PowerNUM_row = 4;
    		final int PowerNum_columns=5;
    		int[][] Powernumbers = new int[PowerNUM_row][PowerNum_columns];
    		Random PowerrandomNumbers = new Random();
    		int Powerrow, Powercolumns=0 ;
     
    		for (Powerrow = 0; Powerrow < 3; Powerrow++)
    			for (Powercolumns = 0; Powercolumns < 1; Powercolumns++)
    				Powernumbers[Powerrow][Powercolumns] = PowerrandomNumbers.nextInt(12);
                    /* now that the loop is over, Powerrow = 3, Powercolumns = 1 */
     
    		for (row = 0; row < 3; row++)
    			for (columns = 0; columns < 5; columns++)
    				numbers[row][columns] = randomNumbers.nextInt(49); 
     
    		System.out.printf("Power Ball Ticket: \n\n");
    		for (row = 0; row < 1; row++)
    		{
    			for (columns = 0; columns < 5; columns++)
    			{
    				System.out.printf("%d ",numbers[row][columns]);
    			}
                            /*
                               Powerrow, Powercolumns not reset, so this prints Powernumbers[3][1]
                               which is never modified after initialization, and therefore 0
                             */
    			System.out.printf("Power Ball: %d", Powernumbers[Powerrow][Powercolumns]);
    			System.out.println();
    		}
    	}
    }
    Hopefully that clears it up for you. I suggest you write cleaner code in the future where your logic is easier to follow. Your loops when generating the Powernumbers modify Powerrow and Powercolumns until they reach 3 and 1, respectively. Since Powernumbers[3][1] is never modified at any intermittent point, the value, when printed, will be that default from initialization i.e. 0.
    Last edited by veeer; July 25th, 2012 at 08:00 AM.

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