```  1  import java.util.Scanner;
2
3  public class CheckSudokuSolution {
4    public static void main(String[] args) {
5      // Read a Sudoku solution
7
8      System.out.println(isValid(grid) ? "Valid solution"
9        : "Invalid solution");
10    }
11
12    /** Read a Sudoku solution from the console */
13    public static int[][] readASolution() {
14      // Create a Scanner
15      Scanner input = new Scanner(System.in);
16
17      System.out.println("Enter a Sudoku puzzle solution:");
18      int[][] grid = new int[9][9];
19      for (int i = 0; i < 9; i++)
20        for (int j = 0; j < 9; j++)
21          grid[i][j] = input.nextInt();
22
23      return grid;
24    }
25
26    /** Check whether a solution is valid */
27    public static boolean isValid(int[][] grid) {
28      for (int i = 0; i < 9; i++)
29        for (int j = 0; j < 9; j++)
30          if (grid[i][j] < 1 || grid[i][j] > 9
31              || !isValid(i, j, grid))
32            return false;
33      return true; // The solution is valid
34    }
35
36    /** Check whether grid[i][j] is valid in the grid */
37    public static boolean isValid(int i, int j, int[][] grid) {
38      // Check whether grid[i][j] is valid at the i's row
39      for (int column = 0; column < 9; column++)
40        if (column != j && grid[i][column] == grid[i][j])
41          return false;
42
43      // Check whether grid[i][j] is valid at the j's column
44      for (int row = 0; row < 9; row++)
45        if (row != i && grid[row][j] == grid[i][j])
46          return false;
47
48      // Check whether grid[i][j] is valid in the 3 by 3 box
49      for (int row = (i / 3) * 3; row < (i / 3) * 3 + 3; row++)
50        for (int col = (j / 3) * 3; col < (j / 3) * 3 + 3; col++)
51          if (row != i && col != j && grid[row][col] == grid[i][j])
52            return false;
53
54      return true; // The current value at grid[i][j] is valid
55    }
56  }
```