title: Java: Declaring a multidimensional array without specifying the size of the array ( eg. new int[10][] )
body: <p>I've been trying to figure out what exactly is happening here. I'm just trying to figure out what the 2 lines are doing that I've commented on below. I found this program that doesn't declare the full dimensions of the array (instead of new int[10][5]; it just decides to not declare it by saying 'new int[10][];' It's like the 2nd array length doesn't matter (changing it to 1 or 100 doesn't affect the output). </p>
  
  <pre><code>int[][] tri = new int[10][];  //this lack of giving the size of the 2nd array is strange
   for (int r=0; r&lt;tri.length; r++) {
   tri[r] = new int[r+1];   //I'm not sure what this line is doing really 
  }
  for (int r=0; r&lt;tri.length; r++) {
   for (int a=0; a&lt;tri[r].length; a++) {
       System.out.print(tri[r][a]);  
       }
   System.out.println();
   }
  </code></pre>