done SudokuCore and Terminal classes,
better interactive mode as follows,

mark@nb:~/zzz/sudoku1$ java -jar target/sudoku1-1.0.jar 000902007_006003900_200067048_900070060_805010739_060030002_710620004_002300100_600701000

 *=============*
 *   Question  *
 *=============*
 --- Sudoku 9x9 --- (start)
 . . . 9 . 2 . . 7
 . . 6 . . 3 9 . .
 2 . . . 6 7 . 4 8
 9 . . . 7 . . 6 .
 8 . 5 . 1 . 7 3 9
 . 6 . . 3 . . . 2
 7 1 . 6 2 . . . 4
 . . 2 3 . . 1 . .
 6 . . 7 . 1 . . .
 --- Sudoku 9x9 --- (end) known cells count: 34
 000902007_006003900_200067048_900070060_805010739_060030002_710620004_002300100_600701000


 *=============*
 *    Answer   *
 *=============*
 --- Sudoku 9x9 --- (start)
 . . . 9 . 2 . . 7
 . . 6 . . 3 9 . .
 2 . . . 6 7 . 4 8
 9 . . . 7 . . 6 .
 8 . 5 . 1 . 7 3 9
 . 6 . . 3 . . . 2
 7 1 . 6 2 . . . 4
 . . 2 3 . . 1 . .
 6 . . 7 . 1 . . .
 --- Sudoku 9x9 --- (end) known cells count: 34
 000902007_006003900_200067048_900070060_805010739_060030002_710620004_002300100_600701000


 *=============*
 *    Status   *
 *=============*
  ...still good

 *=============*
 *   Possible  *
 *=============*
 --- Sudoku 9x9 possible --- (start)
 row#1:{1345},{3458},{1348},{},{458},{},{356},{15},{}
 row#2:{145},{4578},{},{1458},{458},{},{},{125},{15}
 row#3:{},{359},{139},{15},{},{},{35},{},{}
 row#4:{},{234},{134},{2458},{},{458},{458},{},{15}
 row#5:{},{24},{},{24},{},{46},{},{},{}
 row#6:{14},{},{147},{458},{},{4589},{458},{158},{}
 row#7:{},{},{389},{},{},{589},{358},{589},{}
 row#8:{45},{4589},{},{},{4589},{4589},{},{5789},{56}
 row#9:{},{34589},{3489},{},{4589},{},{2358},{2589},{35}
 --- Sudoku 9x9 possible --- (end)  possible count:146
                                       cells count:47

 ...not yet complete, need more arguments to run again

mark@nb:~/zzz/sudoku1$ 3
3: command not found
mark@nb:~/zzz/sudoku1$ java -jar target/sudoku1-1.0.jar 000902007_006003900_200067048_900070060_805010739_060030002_710620004_002300100_600701000 3

 *=============*
 *   Question  *
 *=============*
 --- Sudoku 9x9 --- (start)
 . . . 9 . 2 . . 7
 . . 6 . . 3 9 . .
 2 . . . 6 7 . 4 8
 9 . . . 7 . . 6 .
 8 . 5 . 1 . 7 3 9
 . 6 . . 3 . . . 2
 7 1 . 6 2 . . . 4
 . . 2 3 . . 1 . .
 6 . . 7 . 1 . . .
 --- Sudoku 9x9 --- (end) known cells count: 34
 000902007_006003900_200067048_900070060_805010739_060030002_710620004_002300100_600701000


 *=============*
 *    Answer   *
 *=============*
 --- Sudoku 9x9 --- (start)
 . . . 9 . 2 . . 7
 . . 6 . . 3 9 . .
 2 . . . 6 7 . 4 8
 9 . . . 7 . . 6 .
 8 . 5 . 1 . 7 3 9
 . 6 . . 3 . . . 2
 7 1 . 6 2 . . . 4
 . . 2 3 . . 1 . .
 6 . . 7 . 1 . . .
 --- Sudoku 9x9 --- (end) known cells count: 34
 000902007_006003900_200067048_900070060_805010739_060030002_710620004_002300100_600701000


 *=============*
 *    Status   *
 *=============*
  ...still good

 *=============*
 *   Possible  *
 *=============*
 --- Sudoku 9x9 possible --- (start)
 row#1:{1345},{3458},{1348},{},{458},{},{356},{15},{}
 row#2:{145},{4578},{},{1458},{458},{},{},{125},{15}
 row#3:{},{359},{139},{15},{},{},{35},{},{}
 row#4:{},{234},{134},{2458},{},{458},{458},{},{15}
 row#5:{},{24},{},{24},{},{46},{},{},{}
 row#6:{14},{},{147},{458},{},{4589},{458},{158},{}
 row#7:{},{},{389},{},{},{589},{358},{589},{}
 row#8:{45},{4589},{},{},{4589},{4589},{},{5789},{56}
 row#9:{},{34589},{3489},{},{4589},{},{2358},{2589},{35}
 --- Sudoku 9x9 possible --- (end)  possible count:146
                                       cells count:47


 *=============*
 *   Branch   *
 *=============*
 ... branch #1, assign cell[1]=3

 *=============*
 *    Answer   *
 *=============*
 --- Sudoku 9x9 --- (start)
 3 . . 9 . 2 . . 7
 . . 6 . . 3 9 . .
 2 . . . 6 7 . 4 8
 9 . . . 7 . . 6 .
 8 . 5 . 1 . 7 3 9
 . 6 . . 3 . . . 2
 7 1 . 6 2 . . . 4
 . . 2 3 . . 1 . .
 6 . . 7 . 1 . . .
 --- Sudoku 9x9 --- (end) known cells count: 35
 300902007_006003900_200067048_900070060_805010739_060030002_710620004_002300100_600701000


 *=============*
 *    Status   *
 *=============*
  ...still good

 *=============*
 *   Possible  *
 *=============*
 --- Sudoku 9x9 possible --- (start)
 row#1:{},{458},{148},{},{458},{},{56},{15},{}
 row#2:{145},{4578},{},{1458},{458},{},{},{125},{15}
 row#3:{},{59},{19},{15},{},{},{35},{},{}
 row#4:{},{234},{134},{2458},{},{458},{458},{},{15}
 row#5:{},{24},{},{24},{},{46},{},{},{}
 row#6:{14},{},{147},{458},{},{4589},{458},{158},{}
 row#7:{},{},{389},{},{},{589},{358},{589},{}
 row#8:{45},{4589},{},{},{4589},{4589},{},{5789},{56}
 row#9:{},{34589},{3489},{},{4589},{},{2358},{2589},{35}
 --- Sudoku 9x9 possible --- (end)  possible count:137
                                       cells count:46

 ...not yet complete, need more arguments to run again

mark@nb:~/zzz/sudoku1$ java -jar target/sudoku1-1.0.jar 000902007_006003900_200067048_900070060_805010739_060030002_710620004_002300100_600701000 3 5

 *=============*
 *   Question  *
 *=============*
 --- Sudoku 9x9 --- (start)
 . . . 9 . 2 . . 7
 . . 6 . . 3 9 . .
 2 . . . 6 7 . 4 8
 9 . . . 7 . . 6 .
 8 . 5 . 1 . 7 3 9
 . 6 . . 3 . . . 2
 7 1 . 6 2 . . . 4
 . . 2 3 . . 1 . .
 6 . . 7 . 1 . . .
 --- Sudoku 9x9 --- (end) known cells count: 34
 000902007_006003900_200067048_900070060_805010739_060030002_710620004_002300100_600701000


 *=============*
 *    Answer   *
 *=============*
 --- Sudoku 9x9 --- (start)
 . . . 9 . 2 . . 7
 . . 6 . . 3 9 . .
 2 . . . 6 7 . 4 8
 9 . . . 7 . . 6 .
 8 . 5 . 1 . 7 3 9
 . 6 . . 3 . . . 2
 7 1 . 6 2 . . . 4
 . . 2 3 . . 1 . .
 6 . . 7 . 1 . . .
 --- Sudoku 9x9 --- (end) known cells count: 34
 000902007_006003900_200067048_900070060_805010739_060030002_710620004_002300100_600701000


 *=============*
 *    Status   *
 *=============*
  ...still good

 *=============*
 *   Possible  *
 *=============*
 --- Sudoku 9x9 possible --- (start)
 row#1:{1345},{3458},{1348},{},{458},{},{356},{15},{}
 row#2:{145},{4578},{},{1458},{458},{},{},{125},{15}
 row#3:{},{359},{139},{15},{},{},{35},{},{}
 row#4:{},{234},{134},{2458},{},{458},{458},{},{15}
 row#5:{},{24},{},{24},{},{46},{},{},{}
 row#6:{14},{},{147},{458},{},{4589},{458},{158},{}
 row#7:{},{},{389},{},{},{589},{358},{589},{}
 row#8:{45},{4589},{},{},{4589},{4589},{},{5789},{56}
 row#9:{},{34589},{3489},{},{4589},{},{2358},{2589},{35}
 --- Sudoku 9x9 possible --- (end)  possible count:146
                                       cells count:47


 *=============*
 *   Branch   *
 *=============*
 ... branch #1, assign cell[1]=3

 *=============*
 *    Answer   *
 *=============*
 --- Sudoku 9x9 --- (start)
 3 . . 9 . 2 . . 7
 . . 6 . . 3 9 . .
 2 . . . 6 7 . 4 8
 9 . . . 7 . . 6 .
 8 . 5 . 1 . 7 3 9
 . 6 . . 3 . . . 2
 7 1 . 6 2 . . . 4
 . . 2 3 . . 1 . .
 6 . . 7 . 1 . . .
 --- Sudoku 9x9 --- (end) known cells count: 35
 300902007_006003900_200067048_900070060_805010739_060030002_710620004_002300100_600701000


 *=============*
 *    Status   *
 *=============*
  ...still good

 *=============*
 *   Possible  *
 *=============*
 --- Sudoku 9x9 possible --- (start)
 row#1:{},{458},{148},{},{458},{},{56},{15},{}
 row#2:{145},{4578},{},{1458},{458},{},{},{125},{15}
 row#3:{},{59},{19},{15},{},{},{35},{},{}
 row#4:{},{234},{134},{2458},{},{458},{458},{},{15}
 row#5:{},{24},{},{24},{},{46},{},{},{}
 row#6:{14},{},{147},{458},{},{4589},{458},{158},{}
 row#7:{},{},{389},{},{},{589},{358},{589},{}
 row#8:{45},{4589},{},{},{4589},{4589},{},{5789},{56}
 row#9:{},{34589},{3489},{},{4589},{},{2358},{2589},{35}
 --- Sudoku 9x9 possible --- (end)  possible count:137
                                       cells count:46


 *=============*
 *   Branch   *
 *=============*
 ... branch #2, assign cell[2]=5

 *=============*
 *    Answer   *
 *=============*
 --- Sudoku 9x9 --- (start)
 3 5 8 9 4 2 6 1 7
 4 7 6 1 8 3 9 2 5
 2 9 1 5 6 7 3 4 8
 9 3 4 2 7 5 8 6 1
 8 2 5 4 1 6 7 3 9
 1 6 7 8 3 9 4 5 2
 7 1 3 6 2 8 5 9 4
 5 8 2 3 9 4 1 7 6
 6 4 9 7 5 1 2 8 3
 --- Sudoku 9x9 --- (end) known cells count: 81
 358942617_476183925_291567348_934275861_825416739_167839452_713628594_582394176_649751283


***********************************************
*   This Sudoku question has been solved!!!   *
***********************************************