A Java int-array chess board.

Board.java

import java.util.ArrayList;

public class Board {
	
	public static final int EMPTY	= 0;
	public static final int PAWN	= 1;
	public static final int KNIGHT	= 2;
	public static final int BISHOP	= 3;
	public static final int ROOK	= 4;
	public static final int QUEEN	= 5;
	public static final int KING	= 6;
	
	public static final String FEN_TRANSLATE = "kqrbnp PNBRQK";
	
	private int[][] whiteBoard, blackBoard;
	private boolean whiteMove;
	
	public Board(String fen) {
		whiteMove = true;
		whiteBoard = new int[8][8];
		blackBoard = new int[8][8];
		String[] fenSplit = fen.split(" ");
		String[] fenBoard = fenSplit[0].split("/");
		for(int row = 0; row < 8; row++) {
			String rowS = fenBoard[row];
			for(int pos = 0, col = 0; col < 8; col++, pos++) {
				if(rowS.charAt(pos) < '9')
					col += rowS.charAt(pos) - '1';
				else {
					int let = FEN_TRANSLATE.indexOf(rowS.charAt(pos)) - 6;
					whiteBoard[row][col] = let;
					blackBoard[7 - row][7 - col] = -let;
				}
			}
		}
	}
	
	public void makeMove(String move) {
		char[] mArr = move.toCharArray();
		int sR = mArr[0] - '0', sC = mArr[1] - '0';
		int eR = mArr[2] - '0', eC = mArr[3] - '0';
		int piece = (whiteMove ? 1 : -1) * (mArr[4] - '0');
		whiteBoard[sR][sC] = EMPTY;
		blackBoard[7 - sR][7 - sC] = EMPTY;
		whiteBoard[eR][eC] = piece;
		blackBoard[7 - eR][7 - eC] = -piece;
		whiteMove = !whiteMove;
	}
	
	public void undoMove(String move) {
		char[] mArr = move.toCharArray();
		int sR = mArr[0] - '0', sC = mArr[1] - '0';
		int eR = mArr[2] - '0', eC = mArr[3] - '0';
		int piece = (whiteMove ? 1 : -1) * (mArr[4] - '0');
		int taken = (whiteMove ? -1 : 1) * (mArr[5] - '0');
		whiteBoard[sR][sC] = piece;
		blackBoard[7 - sR][7 - sC] = -piece;
		whiteBoard[eR][eC] = taken;
		blackBoard[7 - eR][7 - eC] = -taken;
		whiteMove = !whiteMove;
	}
	
	public ArrayList<String> getAllMoves() {
		ArrayList<String> moveList = new ArrayList<String>();
		int[][] board = whiteMove ? whiteBoard : blackBoard;
		
		for(int r = 0; r < 8; r++) {
			for(int c = 0; c < 8; c++) {
				switch(board[r][c]) {
				case 1:
					addPawnMoves(r, c, board, moveList);
					break;
				case 2:
					break;
				}
			}
		}
		return moveList;
	}
	
	private void addPawnMoves(int row, int col, int[][] board, ArrayList<String> moveList) {
		if(row == 6 && board[row - 1][col] == EMPTY) {
			moveList.add(row + "" + col + "" + (row - 1) + "" + col + "" + PAWN + "0");
			if(board[row - 2][col] == EMPTY)
				moveList.add(row + "" + col + "" + (row - 2) + "" + col + "" + PAWN + "0");
		}
	}
	
	private void makeMoveString(int sR, int sC, int eR, int eC, int piece, int taken) {
		
	}
	
	public String toString() {
		StringBuilder boardRep = new StringBuilder();
		for(int r = 0; r < 8; r++) {
			boardRep.append(8 - r + "|");a
			for(int c = 0; c < 8; c++)
				boardRep.append(FEN_TRANSLATE.charAt(whiteBoard[r][c] + 6) + "|");
			boardRep.append("\n");
		}
		boardRep.append("  A B C D E F G H");
		return boardRep.toString();
	}
	
	public static void main(String[] args) {
		Board b = new Board("rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1");
		System.out.println(b.getAllMoves());
		b.makeMove("605010");
		System.out.println(b.getAllMoves());
		System.out.println(b);
	}
	
}