Problem The board is maintained in the form of a 2D matrix, which contains the pieces as {color}{type}. Eg. BH : black horse. Pieces: K: king, Q: queen, P: pawn, R: rook, C: bishop, H: horse Move is defined as {color}{type} {src i}{src j} {dest i}{dest j} where i denotes row and j gives column. Eg. BP 12 22, which move black pawn from (1,2) to (2,2).

Implementation: Piece is taken as an abstract class, which is being implemented by the different pieces (classes: King, Rook, Queen, Bishop, Horse, Pawn). Piece has a basic validation rule defined as common. All pieces have their own specific move, and a validation specifc to the piece type. Bishop move is still missing in code. Using Factory design pattern, the object of the specific piece is created, and further movements and validations are performed. Board allows its default, as well as user defined initialization.

Piece class

Pawn class

The other classes ike Rook, King, Queen, etc are also written in the same format, with different validation logic.

MoveImpl class

Main class

Sample Input and Output:

Please suggest the possible improvements in the design.

Problem Description

The board is maintained in the form of a 2D matrix, which contains the pieces as {color}{type}.

Eg. BH : black horse.

Pieces:

• K: king,

• Q: queen,
• P: pawn,
• R: rook,
• C: bishop,
• H: horse

A Move is defined as {color}{type} {src i}{src j} {dest i}{dest j} where \$i\$ denotes row and \$j\$ gives column.
Eg. BP 12 22, which move black pawn from \$(1,2)\$ to \$(2,2)\$.

The Implementation

Piece is taken as an abstract class, which is being implemented by the different pieces King, Rook, Queen, Bishop, Horse, Pawn. A Piece has a basic validation rule defined as common. All pieces have their own specific move, and a validation specific to the piece type. 
Bishop move is still missing in code.

Using Factory design pattern, the object of the specific piece is created, and further movements and validations are performed. Board allows its default, as well as user defined initialization.

Piece class

Pawn class

The other classes like Rook, King, Queen, etc are also written in the same format, with different validation logic.

MoveImpl class

Main class

Sample Input and Output:

Please suggest possible improvements in the design.

I have written a system design code for making Chess Validator, which will validate the moves of a chess game. There is a Main class which is taking the input from the user, about the move.

Github link: https://github.com/yashi320/Chess-Validator

Please suggest the possible improvements in the design system.

I have written code for making a Chess Validator, which will validate the moves of a chess game. There is a Main class which is taking the input from the user, about the move.

Github link: https://github.com/yashi320/Chess-Validator

Please suggest the possible improvements in the design.

Github link: https://github.com/yashi320/Chess-Validator

Input:
Display

INITIAL STATE:
CURRENT BOARD:
BR BH BC BK BQ BC BH BR 
BP BP BP BP BP BP BP BP 
-- -- -- -- -- -- -- -- 
-- -- -- -- -- -- -- -- 
-- -- -- -- -- -- -- -- 
-- -- -- -- -- -- -- -- 
WP WP WP WP WP WP WP WP 
WR WH WC WQ WK WC WH WR 
Moves
BP 12 32
CURRENT BOARD:
BR BH BC BK BQ BC BH BR 
BP BP -- BP BP BP BP BP 
-- -- -- -- -- -- -- -- 
-- -- BP -- -- -- -- -- 
-- -- -- -- -- -- -- -- 
-- -- -- -- -- -- -- -- 
WP WP WP WP WP WP WP WP 
WR WH WC WQ WK WC WH WR 
BP 32 12
Invalid move
CURRENT BOARD:
BR BH BC BK BQ BC BH BR 
BP BP -- BP BP BP BP BP 
-- -- -- -- -- -- -- -- 
-- -- BP -- -- -- -- -- 
-- -- -- -- -- -- -- -- 
-- -- -- -- -- -- -- -- 
WP WP WP WP WP WP WP WP 
WR WH WC WQ WK WC WH WR 
WP 61 51
CURRENT BOARD:
BR BH BC BK BQ BC BH BR 
BP BP -- BP BP BP BP BP 
-- -- -- -- -- -- -- -- 
-- -- BP -- -- -- -- -- 
-- -- -- -- -- -- -- -- 
-- WP -- -- -- -- -- -- 
WP -- WP WP WP WP WP WP 
WR WH WC WQ WK WC WH WR 
BP 32 42
CURRENT BOARD:
BR BH BC BK BQ BC BH BR 
BP BP -- BP BP BP BP BP 
-- -- -- -- -- -- -- -- 
-- -- -- -- -- -- -- -- 
-- -- BP -- -- -- -- -- 
-- WP -- -- -- -- -- -- 
WP -- WP WP WP WP WP WP 
WR WH WC WQ WK WC WH WR 
WP 51 42
CURRENT BOARD:
BR BH BC BK BQ BC BH BR 
BP BP -- BP BP BP BP BP 
-- -- -- -- -- -- -- -- 
-- -- -- -- -- -- -- -- 
-- -- WP -- -- -- -- -- 
-- -- -- -- -- -- -- -- 
WP -- WP WP WP WP WP WP 
WR WH WC WQ WK WC WH WR 
WP 42 52
Invalid move
CURRENT BOARD:
BR BH BC BK BQ BC BH BR 
BP BP -- BP BP BP BP BP 
-- -- -- -- -- -- -- -- 
-- -- -- -- -- -- -- -- 
-- -- WP -- -- -- -- -- 
-- -- -- -- -- -- -- -- 
WP -- WP WP WP WP WP WP 
WR WH WC WQ WK WC WH WR 
WP 62 52
CURRENT BOARD:
BR BH BC BK BQ BC BH BR 
BP BP -- BP BP BP BP BP 
-- -- -- -- -- -- -- -- 
-- -- -- -- -- -- -- -- 
-- -- WP -- -- -- -- -- 
-- -- WP -- -- -- -- -- 
WP -- -- WP WP WP WP WP 
WR WH WC WQ WK WC WH WR 
WQ 73 50
Invalid move
CURRENT BOARD:
BR BH BC BK BQ BC BH BR 
BP BP -- BP BP BP BP BP 
-- -- -- -- -- -- -- -- 
-- -- -- -- -- -- -- -- 
-- -- WP -- -- -- -- -- 
-- -- WP -- -- -- -- -- 
WP -- -- WP WP WP WP WP 
WR WH WC WQ WK WC WH WR 
WQ 73 40
CURRENT BOARD:
BR BH BC BK BQ BC BH BR 
BP BP -- BP BP BP BP BP 
-- -- -- -- -- -- -- -- 
-- -- -- -- -- -- -- -- 
WQ -- WP -- -- -- -- -- 
-- -- WP -- -- -- -- -- 
WP -- -- WP WP WP WP WP 
WR WH WC -- WK WC WH WR 
WQ 40 13
CURRENT BOARD:
BR BH BC BK BQ BC BH BR 
BP BP -- WQ BP BP BP BP 
-- -- -- -- -- -- -- -- 
-- -- -- -- -- -- -- -- 
-- -- WP -- -- -- -- -- 
-- -- WP -- -- -- -- -- 
WP -- -- WP WP WP WP WP 
WR WH WC -- WK WC WH WR 
WP 52 32
Invalid move
CURRENT BOARD:
BR BH BC BK BQ BC BH BR 
BP BP -- WQ BP BP BP BP 
-- -- -- -- -- -- -- -- 
-- -- -- -- -- -- -- -- 
-- -- WP -- -- -- -- -- 
-- -- WP -- -- -- -- -- 
WP -- -- WP WP WP WP WP 
WR WH WC -- WK WC WH WR 
WH 71 53
Invalid move
CURRENT BOARD:
BR BH BC BK BQ BC BH BR 
BP BP -- WQ BP BP BP BP 
-- -- -- -- -- -- -- -- 
-- -- -- -- -- -- -- -- 
-- -- WP -- -- -- -- -- 
-- -- WP -- -- -- -- -- 
WP -- -- WP WP WP WP WP 
WR WH WC -- WK WC WH WR 
WH 71 52
Invalid move: Your color piece at that place
Invalid move
CURRENT BOARD:
BR BH BC BK BQ BC BH BR 
BP BP -- WQ BP BP BP BP 
-- -- -- -- -- -- -- -- 
-- -- -- -- -- -- -- -- 
-- -- WP -- -- -- -- -- 
-- -- WP -- -- -- -- -- 
WP -- -- WP WP WP WP WP 
WR WH WC -- WK WC WH WR 
WH 71 50
CURRENT BOARD:
BR BH BC BK BQ BC BH BR 
BP BP -- WQ BP BP BP BP 
-- -- -- -- -- -- -- -- 
-- -- -- -- -- -- -- -- 
-- -- WP -- -- -- -- -- 
WH -- WP -- -- -- -- -- 
WP -- -- WP WP WP WP WP 
WR -- WC -- WK WC WH WR 

Piece class

public abstract class Piece {

private char color;

public char getColor() {
    return color;
}

public void setColor(char color) {
    this.color = color;
}


public abstract boolean validateForPiece(int srcX, int srcY, int destX, int destY);

public void move(int srcX, int srcY, int destX, int destY, String piece) {
    Board.CHESS_BOARD[destX][destY]=piece;
    Board.CHESS_BOARD[srcX][srcY]="--";
}

public boolean checkMiddlePieces(int srcX, int srcY, int destX, int destY) {
    if(srcX==destX && srcY!=destY) {
        for(int i=srcY+1;i<destY;i++) {
            if(Board.CHESS_BOARD[destX][i]!="--")
                return false;
        }
    }
    else if(srcX!=destX && srcY==destY) {
        for(int i=srcX+1;i<destX;i++) {
            if(Board.CHESS_BOARD[i][destY]!="--")
                return false;
        }
    }
    else if(Math.abs(srcX-destX)==Math.abs(srcY-destY)) {
        for(int i=srcX+1,j=srcY+1;i<destX && j<destY;i++,j++) {
            if(Board.CHESS_BOARD[i][destY]!="--")
                return false;
        }
    }
    return true;
}

public boolean validateFirst(int srcX, int srcY, int destX, int destY, String piece) {
    char color = piece.charAt(0);
    if(srcX>=8 || destX>=8 || srcY>=8 || destY>=8) {
        System.out.println("Exception handled");
        return false;
    }
    if(Board.CHESS_BOARD[srcX][srcY].equals("--")) {
        System.out.println("Invalid move: No piece in this place");
        return false;
    }
    if(!Board.CHESS_BOARD[srcX][srcY].equals(piece)) {
        System.out.println("Invalid move: Different piece at given source");
        return false;
    }
    if(Board.CHESS_BOARD[destX][destY]!="--") {
        if(Board.CHESS_BOARD[destX][destY].charAt(0)==color) {
            System.out.println("Invalid move: Your color piece at that place");
            return false;
        }
    }
    return true;
}
}

Pawn class

public class Pawn extends Piece {

@Override
public boolean validateForPiece(int srcX, int srcY, int destX, int destY) {
    if(Board.TOP_WHITE) {
        if(this.getColor()=='W' && destX-srcX<0)
            return false;
        if(this.getColor()=='B' && destX-srcX>0)
            return false;
    }
    else {
        if(this.getColor()=='B' && destX-srcX<0)
            return false;
        if(this.getColor()=='W' && destX-srcX>0)
            return false;
    }
    if(((srcX==1 || srcX==6) && (Math.abs(destX-srcX)==2)) 
            || ((srcX!=1 || srcX!=6) && (Math.abs(destX-srcX)==1)) 
            && srcY==destY) {
        return true;
    }
    if(Math.abs(srcY-destY)==1) {
        if(Board.CHESS_BOARD[destX][destY]=="--")
        return true;
    }
    if(Math.abs(srcX-destX)==1 && Math.abs(srcY-destY)==1) {
        return true;
    }
    return false;
}
}

The other classes ike Rook, King, Queen, etc are also written in the same format, with different validation logic.

MoveImpl class

public class MoveImpl implements Move {

String piece;
int srcX;
int srcY;
int destX;
int destY;
char color;
char pieceType;

private void initializeValues(String inputMove[]) {
    piece = inputMove[0];
    srcX = Integer.parseInt(""+inputMove[1].charAt(0));
    srcY = Integer.parseInt(""+inputMove[1].charAt(1));
    destX = Integer.parseInt(""+inputMove[2].charAt(0));
    destY = Integer.parseInt(""+inputMove[2].charAt(1));
    color = piece.charAt(0);
    pieceType = piece.charAt(1);
    
}


@Override
public void move(String inputMove[]) {
    initializeValues(inputMove);
    Piece pieceObj = PieceFactory.getPiece(piece);
    boolean check1=pieceObj.validateFirst(srcX, srcY, destX, destY, piece);
    boolean check2=pieceObj.validateForPiece(srcX, srcY, destX, destY);
    if(!check1 || !check2)
        System.out.println("Invalid move");
    if(check1 && check2)
        pieceObj.move(srcX, srcY, destX, destY, piece);
}
}

Main class

public class Main {

public static void main(String[] args) throws IOException {
    
    Move move = new MoveImpl();
    System.out.println("Input:");
    BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
    String inp = br.readLine();
    if(inp.equals("Board")) {
        String board[][] = new String[8][8];
        for(int i=0;i<8;i++) {
            String row = br.readLine();
            String rowArr[]=row.split(" ");
            if(row.trim()!="")
            for(int j=0;j<8;j++) {
                board[i][j] = rowArr[j];
            }
        }
        BoardInitializer.initialize(board);
        System.out.println();
        System.out.println("INITIAL STATE:");
        BoardInitializer.displayBoardState();
    }
    else if(inp.equals("Display")) {
        BoardInitializer.initialize();
        System.out.println();
        System.out.println("INITIAL STATE:");
        BoardInitializer.displayBoardState();
    }
    inp=br.readLine();
    if(inp.equals("Moves")){
        while(inp!=null && inp.trim()!="") {
            if(inp.trim().equals(""))
                break;
            inp = br.readLine();
            if(inp.trim().equals(""))
                break;
            String inputMove[]=inp.split(" ");
            move.move(inputMove);

            BoardInitializer.displayBoardState();
        }
    }
}
}

Github link: https://github.com/yashi320/Chess-Validator

Input:
Display

INITIAL STATE:
CURRENT BOARD:
BR BH BC BK BQ BC BH BR 
BP BP BP BP BP BP BP BP 
-- -- -- -- -- -- -- -- 
-- -- -- -- -- -- -- -- 
-- -- -- -- -- -- -- -- 
-- -- -- -- -- -- -- -- 
WP WP WP WP WP WP WP WP 
WR WH WC WQ WK WC WH WR 
Moves
BP 12 32
CURRENT BOARD:
BR BH BC BK BQ BC BH BR 
BP BP -- BP BP BP BP BP 
-- -- -- -- -- -- -- -- 
-- -- BP -- -- -- -- -- 
-- -- -- -- -- -- -- -- 
-- -- -- -- -- -- -- -- 
WP WP WP WP WP WP WP WP 
WR WH WC WQ WK WC WH WR 
BP 32 12
Invalid move
CURRENT BOARD:
BR BH BC BK BQ BC BH BR 
BP BP -- BP BP BP BP BP 
-- -- -- -- -- -- -- -- 
-- -- BP -- -- -- -- -- 
-- -- -- -- -- -- -- -- 
-- -- -- -- -- -- -- -- 
WP WP WP WP WP WP WP WP 
WR WH WC WQ WK WC WH WR