Algorithm complexity of this program is O(n) or O(n^3)?

Question

I am very much confuse that why complexity of this program is O(n)?

 int j = 0;
 int i;
 For (i = 0; i < n, i++) // O(n)
 {
      For (i = 0; i < n, i++)//O(n)
      {
        While (j < n)// O(n)
       {
        Statement; j++;
       }
   }    
 }

I am totally new to Algorithms. Any help and explanation will be appreciated.