Sudoku Solver

Write a program to solve a Sudoku puzzle by filling the empty cells.

Empty cells are indicated by the character '.'.

public class Solution {
    public void solveSudoku(char[][] board) {
        solve(board);
    }
    public boolean solve(char[][]board){
        for(int i=0;i<9;i++){
            for(int j=0;j<9;j++){
                if(board[i][j]=='.'){
                    for(int k=1;k<=9;k++){
                        board[i][j]=(char) (k+'0');
                        if(isValid(board,i,j) && solve(board))
                            return true;
                        else {
                                board[i][j] = '.';
                        }
                    }
                    return false;
                }
            }
        }
        return true;
    }
    public boolean isValid(char[][]board,int x,int y){
        for(int i=0;i<board.length;i++){
            if(x!=i && board[x][y]==board[i][y]) return false;
        }
        for(int i=0;i<board.length;i++){
            if(y!=i && board[x][y]==board[x][i]) return false;
        }
        for(int i=3*(x/3);i<3*(x/3+1);i++){
            for(int j=3*(y/3);j<3*(y/3+1);j++){
                if(x!=i &&j!=y &&board[i][j]==board[x][y]) return false;
            }
        }
        return true;
    }
    }