title: What should I do if I don't know the length of array beforehand?
body: <p>This is my java code:</p>
  <pre><code>class soduku
  {
      int[][] board ={
           {8, 0, 0, 0, 0, 0, 0, 0, 0},
           {0, 0, 3, 6, 0, 0, 0, 0, 0},
           {0, 7, 0, 0, 9, 0, 2, 0, 0},
           {0, 5, 0, 0, 0, 7, 0, 0, 0},
           {0, 0, 0, 0, 4, 5, 7, 0, 0},
           {0, 0, 0, 1, 0, 0, 0, 3, 0},
           {0, 0, 1, 0, 0, 0, 0, 6, 8},
           {0, 0, 8, 5, 0, 0, 0, 1, 0},
           {0, 9, 0, 0, 0, 0, 4, 0, 0}};
      int[][] mutable = mutable();
      int[][] mutable()
      {
          int i,j;
          int count = 0;
          for(i=0;i&lt;board.length;i++)
          {
              for(j=0; j&lt;board[i].length;j++)
              if (board[i][j] == 0)
              count++;
          }
          int [][] mutable = new int[count][2];
          int k = 0;
          for(i=0;i&lt;board.length;i++)
          {
              for(j=0; j&lt;board[i].length; j++)
              {
                  if(board[i][j]==0)
                  {
                      mutable[k][0]=i;
                      mutable[k][1]=j;
                      k++;
                  }
              }
          }
          return mutable;
      }
  }
  </code></pre>
  <p>As you can see I have to count the number of zeroes so that I can declare the array mutable.
  I want to know if there's a better way so that could do the same thing. I am new to Java and only know about arrays and some basic data type.</p>