private List<Column> createColumnList(NQueens nQueens) {
int n = nQueens.getN();
List<Column> columnList = new ArrayList<Column>(n);
for (int i = 0; i < n; i++) {
Column column = new Column();
column.setId((long) i);
column.setIndex(i);
columnList.add(column);
}
return columnList;
}