2-dimensional arrays

2-dimensional arrays

In this code snippet:

Code :

---

public static int[][] pascalTriangle(int n) {
  int[][] pt = new int[n][];
  for (int i = 0; i < n; i++) {
     pt[i] = new int[i + 1];                   
     pt[i][0] = 1;                              
     for (int j = 1; j < i; j++) {
       pt[i][j] = pt[i - 1][j - 1] + pt[i - 1][j]; 
     }
     pt[i][i] = 1;         
   }
   return pt;
}

---

in the second live, we specify a length for the one dimesnion, but for the second dimension, its just open and close brackets. How is it possible to do that, to be able to declare a two-dimensional array like that without specifying a length? I thought an array had to have an exact length when initialized before you could actually assign items to it.