Connect Four

import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;

class ConnectFour {

    char winner;
    int move;

    // four adjacent points
    String one;
    String two;
    String three;
    String four;

    public ConnectFour(List<String> moves) {
        char[][] board = new char[6][7];
        int move = 0;
        for (String m : moves) {
            move++;
            board = set(board, m.charAt(0));
            if (isWinner(board)) {
                this.winner = 'X';
                break;
            }
            board = set(board, m.charAt(1));
            if (isWinner(board)) {
                this.winner = 'O';
                break; // double check to account for a situation where both players would win in the same turn
            }
        }

        this.move = move;

        if(winner == 0) {
            System.out.println(printboard(board) + "\n\nNo Winner\n");
            return;
        }

        System.out.println(printboard(board) + "\n");
        System.out.print(String.format("%s won at move %d (with %s %s %s %s)",
                this.winner, this.move, this.one, this.two, this.three, this.four));
    }


    private static char[][] set(char[][] board, char c) {
        char player = Character.isUpperCase(c) ? 'X' : 'O';
        int col = 5;
        int row = (int) Character.toUpperCase(c) - 65;
        while (board[col][row] != 0) {
            col--;
        }
        board[col][row] = player;
        return board;
    }

    private static boolean bingo(char a, char b, char c, char d) {
        return a != 0 && b != 0 && c != 0 && d != 0
                && a == b && b == c && c == d;
    }

    private boolean isWinner(char[][] board) {
        // horizontally
        for (int i = 0; i < 6; i++) {
            for (int j = 0; j < 4; j++) {
                char one = board[i][j];
                char two = board[i][j + 1];
                char three = board[i][j + 2];
                char four = board[i][j + 3];
                if (bingo(one, two, three, four)) {
                    this.one = coordToPoint(i, j);
                    this.two = coordToPoint(i, j + 1);
                    this.three = coordToPoint(i, j + 2);
                    this.four = coordToPoint(i, j + 3);
                    return true;
                }
            }
        }

        // vertically
        for (int i = 5; i > 2; i--) {
            for (int j = 0; j < 7; j++) {
                char one = board[i][j];
                char two = board[i - 1][j];
                char three = board[i - 2][j];
                char four = board[i - 3][j];
                if (bingo(one, two, three, four)) {
                    this.one = coordToPoint(i, j);
                    this.two = coordToPoint(i - 1, j);
                    this.three = coordToPoint(i - 2, j);
                    this.four = coordToPoint(i - 3, j);
                    return true;
                }
            }
        }

        // diagonally top left -> bottom right
        for (int i = 0; i < 3; i++) {
            for (int j = 0; j < 4; j++) {
                char one = board[i][j];
                char two = board[i + 1][j + 1];
                char three = board[i + 2][j + 2];
                char four = board[i + 3][j + 3];
                if (bingo(one, two, three, four)) {
                    this.one = coordToPoint(i, j);
                    this.two = coordToPoint(i + 1, j + 1);
                    this.three = coordToPoint(i + 2, j + 2);
                    this.four = coordToPoint(i + 3, j + 3);
                    return true;
                }
            }
        }

        // diagonally top right -> bottom left
        for (int i = 5; i > 2; i--) {
            for (int j = 0; j < 4; j++) {
                char one = board[i][j];
                char two = board[i - 1][j + 1];
                char three = board[i - 2][j + 2];
                char four = board[i - 3][j + 3];
                if (bingo(one, two, three, four)) {
                    this.one = coordToPoint(i, j);
                    this.two = coordToPoint(i - 1, j + 1);
                    this.three = coordToPoint(i - 2, j + 2);
                    this.four = coordToPoint(i - 3, j + 3);
                    return true;
                }
            }
        }

        return false;
    }

    private static String coordToPoint(int i, int j) {
        return (char) (j + 65) + String.valueOf((6 - i));
    }

    private static String printboard(char[][] board) {
        String strBoard = "\n  A B C D E F G\n";
        for (int i = 0; i < board.length; i++) {
            if (i != 0) {
                strBoard += "\n";
            }
            strBoard += (6 - i) + " ";
            for (int j = 0; j < board[i].length; j++) {
                char c = board[i][j];
                strBoard += c == 0 ? ". " : c + " ";
            }
        }
        return strBoard;
    }
}

public class Main {
    public static void main (String args[]) {
        List<String> moves = new ArrayList<>();
        Scanner scanner = new Scanner(System.in);
        while(scanner.hasNext()) {
            String move = scanner.nextLine().replaceAll("\\s", "");
            if(!Character.isUpperCase(move.charAt(0)) || !Character.isLowerCase(move.charAt(1))) {
                System.out.print("Try again: ");
                continue;
            }
            try {
                moves.add(move);
                new ConnectFour(moves);
            } catch (ArrayIndexOutOfBoundsException aioobe) {
                moves.remove(moves.size() - 1);
                System.out.print("Try again: ");
            }
        }
    }
}