File picker now refuses to load unsolvable files

app/src/main/java/gui/SudokuController.java

@@ -26,13 +26,13 @@ public class SudokuController {
             public void actionPerformed(ActionEvent e) {
                 // Solve the board
                 boolean solved = model.solve();
+                // Update the view
+                view.updateView(model.getBoard());
                 if (!solved) {
                     view.showErrorMessage("Could not solve the board.");
                     System.out.println("Could not solve the board.");
                     System.out.println(model.toString());
                 } else {
-                    // Update the view
-                    view.updateView(model.getBoard());
                 }
 
             }
@@ -70,6 +70,13 @@ public class SudokuController {
                 if (newBoard != null) {
                     // Set the model
                     model.setBoard(newBoard);
+
+                    // Warn and clear if the board is not solvable
+                    if(!model.isSolvable()) {
+                        view.showErrorMessage("The board is not solvable.");
+                        model.clear();
+                    }
+
                     // Update the view
                     view.updateView(model.getBoard());
                 }
@@ -113,7 +120,7 @@ public class SudokuController {
             }
 
             // If the input is invalid, value < 0 indicates parse error
-            if (!model.isLegal(row, col, value) || value < 0) {
+            if (value != 0 && !model.isLegal(row, col, value) || value < 0) {
                 value = 0;
                 view.showErrorMessage("Invalid input. Try again.");
             }

app/src/main/java/sudoku/Solver.java

@@ -29,7 +29,12 @@ public class Solver implements SudokuSolver {
     /** Resets the board to all zeros */
     @Override
     public void clear() {
-        board = new int[9][9];
+        for (int[] row : board) {
+            for (int i = 0; i < row.length; ++i) {
+                row[i] = 0;
+            }
+        }
+        // board = new int[9][9];
     }
 
     /* {@inheritDoc} */
@@ -144,6 +149,11 @@ public class Solver implements SudokuSolver {
             return false;
         }
 
+        // Ihe the number is already present in the cell
+        if (board[row][col] == num) {
+            return true;
+        }
+
         // Check both the row and column
         for (int i = 0; i < 9; i++) {
             if (board[row][i] == num || board[i][col] == num) {