Two dimentional arrays (distinguishing the columns from the rows)?

Question

I am a novice to java. Im trying to write a two-dementional array that writes out a lottery ticket (6 integers) 10 times

int[][] lottery = new int[6][10];

for (int i=0; i < lottery.length; i++)
 for (int j=0; j < lottery[0].length; j++)  
  lottery[i][j] = (int)(50.0 * Math.random());

for (int i=0; i < lottery.length; i++)
 for (int j=0; j < lottery[0].length; j++)      
 {
  /*if i < lottery.length
  System.out.print(lottery[i][j] + " ");
  else
  System.out.println(lottery[i][j]);*/
 }  

How do I write it out as 10 rows of 6 integers

23 12 31 49 3 17 
9 1 22 13 36 50
.
.
.

Answer 1

Your array is backwards. If you want to be able to output 10 rows of 6 numbers with the nested for loops that you have, you would need the array to be int lottery[][] = new int[10][6];

Then to output it, you'd simply need to do:

for (int i=0; i < lottery.length; i++){
 for (int j=0; j < lottery[i].length; j++){
    System.out.print(lottery[i][j]+"");
    if(j < lottery[i].length -1){
      System.out.print(" ");
    }
 }
 System.out.print("\n");
} 

The call to System.out.print will print the text without a new-line character so you can keep appending to the same line.

Answer 2

Java (like C), stores multidimensional arrays in Row-major order . Depending on your mindset this may seem natural or not but just remember arrays are referenced by [row][col] , not [col][row] .

Your array int[][] lottery = new int[6][10]; is 6 rows, 10 cols each. Based on your description, I think you want 10 rows or 6 cols each or int[][] lottery = new int[10][6];

Then print it:

for (int i=0; i < lottery.length; i++) 
{
     for (int j=0; j < lottery[0].length; j++)      
     {
          if (j < (lottery[0].length+1)
          { 
              System.out.print(lottery[i][j] + " ");
          }
          else
          {
              System.out.println(lottery[i][j]);
          }
     } 
 }

Answer 3

10 rows of 6 integers:

int[][] lottery = new int[10][6];

Formatted printing:

for(int row=0; row<nums.length; row++) {
    for(int col=0; col<nums[row].length; col++) {
        System.out.printf("%2d", nums[row][col]);
    }
    System.out.print("\n");
}

Go through the title "Format String Syntax" here.