in android/tutorials/tutorial4/src/main/java/com/uber/rib/root/loggedin/tictactoe/Board.java [40:49]
boolean isDraw() {
for (int row = 0; row < ROWS; ++row) {
for (int col = 0; col < COLS; ++col) {
if (cells[row][col] == null) {
return false;
}
}
}
return !hasWon(MarkerType.CROSS) && !hasWon(MarkerType.NOUGHT);
}