int n = 1;
ArrayList list = new ArrayList();
list.add( n );

grid[ y ][ x ] = list.get(0);

grid[ y ][ x ] = (int) list.get(0);

found   : java.lang.Object
required: int
grid[ y ][ x ] = (int)list.get(0);
                              ^

ArrayList<Integer> list = new ArrayList<Integer>();