Java: 2D array of arraylists? -

i working on sudoku solving program , need arraylist holds numbers 1 thru 9 each of squares on 9x9 board. each of these arraylists correspond possible numbers go in square, if number can not go in square, removed list.

i want able pull arraylist of current square working on, example if wanted remove number 7 arraylist corresponding square (3,5)

arrayoflists[3][5].remove(integer.valueof(7)); 

however can't figure out how this. when try create array getting error on line declare array of arraylists

cannot create generic array of arraylist

here code:

    //create arraylist     arraylist<integer> nums = new arraylist<integer>();      //fill arraylist numbers 1-9     (int = 1; < 10; i++) {         nums.add(i);     }      //create 9x9 array of arraylists     arraylist<integer>[][] array = new arraylist<integer>[9][9];      //fill each element of array arraylist of numbers 1-9     for(int = 0; i<9; i++){         for(int j = 0; j<9; j++){             array[i][j] = nums;         }            }  } 

am doing incorrectly or not possible create array of arraylists? if not possible, how should then?

anytime see list of lists, alarm bells start ringing. situations want such thing rare indeed, , not 1 of them.

you've got fixed board consisting of 9 fixed squares, columns , rows, each position of may take number 1-9.

use array of these concepts, because fixed in size , need direct access each element - collections offer no benefit , hindrance. use logic (possibly sets) ensure numbers used once in each zone.