Board.java

public class Board {

    public static char EMPTY = '.';

    private int N, M;
    private char[][] data;

    public Board(String[] lines){
        if(lines == null)
            throw new IllegalArgumentException("lines cannot be null in Board constructor.");

        N = lines.length;
        if(N == 0)
            throw new IllegalArgumentException("lines cannot be empty in Board constructor.");

        M = lines[0].length();

        data = new char[N][M];
        for(int i = 0 ; i < N ; i ++){
            if(lines[i].length() != M)
                throw new IllegalArgumentException("All lines' length must be same in Board constructor.");
            for(int j = 0 ; j < M ; j ++)
                data[i][j] = lines[i].charAt(j);
        }
    }

    public Board(Board board){
        if(board == null)
            throw new IllegalArgumentException("board can not be null in Board constructor!");

        this.N = board.N;
        this.M = board.M;
        this.data = new char[N][M];
        for(int i = 0 ; i < N ; i ++)
            for(int j = 0 ; j < M ; j ++)
                this.data[i][j] = board.data[i][j];
    }

    public int N(){ return N; }
    public int M(){ return M; }
    public char getData(int x, int y){
        if(!inArea(x, y))
            throw new IllegalArgumentException("x, y are out of index in getData!");

        return data[x][y];
    }

    public boolean inArea(int x, int y){
        return x >= 0 && x < N && y >= 0 && y < M;
    }

    public void print(){
        for(int i = 0 ; i < N ; i ++)
            System.out.println(String.valueOf(data[i]));
    }

    public boolean isWin(){

        for(int i = 0 ; i < N ; i ++)
            for(int j = 0 ; j < M ; j ++)
                if(data[i][j] != EMPTY)
                    return false;

        return true;
    }

    public void swap(int x1, int y1, int x2, int y2){

        if(!inArea(x1, y1) || !inArea(x2, y2))
            throw new IllegalArgumentException("x, y are out of index in swap!");

        char t = data[x1][y1];
        data[x1][y1] = data[x2][y2];
        data[x2][y2] = t;

        return;
    }

    public void run(){

    }
}