Suitable exceptions for setBoard with corresponding tests

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

@@ -12,7 +12,11 @@ public class Solver implements SudokuSolver {
 
     /** {@inheritDoc} */
     @Override
-    public void setBoard(int[][] board) {
+    public void setBoard(int[][] board) throws IllegalArgumentException, NullPointerException {
+        if (board == null)
+            throw new NullPointerException("Board cannot be null");
+        if (board.length != 9 || board[0].length != 9)
+            throw new IllegalArgumentException("Board must be 9x9");
         this.board = board;
     }
 
@@ -107,7 +111,7 @@ public class Solver implements SudokuSolver {
         }
 
         // Recursively call randomizeBoard() until we get a solvable board
-        // This is expensive, and there should be some voodoo magic that computes this in n^2 time
+        // This is expensive, and there should be a better way to do this
         if (!isSolvable()) {
             randomizeBoard(difficulty);
         }

app/src/main/java/sudoku/SudokuSolver.java

@@ -1,5 +1,6 @@
 package sudoku;
 
+/** SudokuSolver is an interface for implementing Sudoku solvers */
 public interface SudokuSolver {
     /**
      * Set sudoku board, numbers 1-9 are fixed values, 0 is unsolved.
@@ -7,10 +8,12 @@ public interface SudokuSolver {
      * @param board a board to copy values from
      * @throws IllegalArgumentException if board is invalid, e.g. not 9x9
      */
-    void setBoard(int[][] board) throws IllegalArgumentException;
+    void setBoard(int[][] board) throws IllegalArgumentException, NullPointerException;
 
     /**
      * Get a copy of the sudoku board
+     * 
+     * @return a <b>copy</b> of the sudoku board
      */
     int[][] getBoard();
 
@@ -24,9 +27,9 @@ public interface SudokuSolver {
     /**
      * Check if digit is legal on the current board
      * 
-     * @param row
+     * @param row row
-     * @param col
+     * @param col column
-     * @param nbr
+     * @param nbr number to check
      * @return true if legal
      */
     boolean isLegal(int row, int col, int nbr);
@@ -34,8 +37,8 @@ public interface SudokuSolver {
     /**
      * Get number on board
      * 
-     * @param row
+     * @param row row
-     * @param col
+     * @param col column
      * @return number on board
      */
     int get(int row, int col);
@@ -43,9 +46,9 @@ public interface SudokuSolver {
     /**
      * Set number on board, numbers 1-9 are fixed values, 0 is unsolved.
      * 
-     * @param row
+     * @param row row
-     * @param col
+     * @param col column
-     * @param nbr
+     * @param nbr number to set
      */
     void set(int row, int col, int nbr);
 

app/src/test/java/sudoku/SolverTest.java

@@ -106,4 +106,11 @@ class SolverTest {
         solver.set(7, 1, 8);
         assertFalse(solver.solve());
     }
+
+    @Test
+    void setBoardInvalidInputThrowsTest() {
+        Solver solver = new Solver();
+        assertThrows(NullPointerException.class, () -> solver.setBoard(null));
+        assertThrows(IllegalArgumentException.class, () -> solver.setBoard(new int[8][8]));
+    }
 }