public class Connect4 {

     char[][] board = new char[][];

     public Connect4(char[][] board) {

         this.board = board;

     }

     public static void main(String[] args) {

         Connect4 game = new Connect4(new char[][]);

         game.fillBoard(' ');

         Scanner input = new Scanner(System.in);

         char player = 'X';

         while (true) {

             game.showGameBoard();

             System.out.print("Player " + player + ", please enter the column where you'd like to drop your piece: ");

             int col = input.nextInt();

             if (game.tryDropPiece(col, player)) {

                 if (game.checkForWin()) {

                     System.out.println("Player " + player + " wins!");

                     game.showGameBoard();

                     return;

                 }

                 player = game.switchPlayer(player); // Switch players

             }

         }

     }

     public char[][] fillBoard(char myChar) {

         for (int row = ; row < board.length; row++) {

             Arrays.fill(board[row], , board[row].length, myChar);

         }

         return board;

     }

     public void showGameBoard() {

         System.out.println();

         for (int row = ; row < board.length; row++) {

             System.out.print("|");

             for (int col = ; col < board[row].length; col++) {

                 System.out.print(" " + board[row][col] + " |");

             }

             System.out.println();

         }

     }

     public boolean tryDropPiece(int col, char player) {

         if (board[][col] != ' ') {

             System.out.println("That column is already full.");

             return false;

         }

         for (int row = board.length - ; row >= ; row--) {

             if (board[row][col] == ' ') {

                 board[row][col] = player;

                 return true;

             }

         }

         return false;

     }

     public boolean checkForWin() {

         boolean result = false;

         // Check for win horizontally

         for (int row = ; row < board.length; row++) {

             for (int col = ; col < board[row].length - ; col++) {

                 if (board[row][col] != ' ' && board[row][col] == board[row][col + ]

                         && board[row][col] == board[row][col + ] && board[row][col] == board[row][col + ]) {

                     return true;

                 }

             }

         }

         // Check for win vertically

         for (int col = ; col < board[].length; col++) {

             for (int row = ; row < board.length - ; row++) {

                 if (board[row][col] != ' ' && board[row][col] == board[row + ][col]

                         && board[row][col] == board[row + ][col] && board[row][col] == board[row + ][col]) {

                     return true;

                 }

             }

         }

         // Check for win diagonally, from top left

         for (int row = ; row < board.length - ; row++) {

             for (int col = ; col < board[row].length - ; col++) {

                 if (board[row][col] != ' ' && board[row][col] == board[row + ][col + ]

                         && board[row][col] == board[row + ][col + ] && board[row][col] == board[row + ][col + ]) {

                     return true;

                 }

             }

         }

         // Check for win diagonally, from top right

         for (int row = ; row < board.length - ; row++) {

             for (int col = ; col < board[row].length; col++) {

                 if (board[row][col] != ' ' && board[row][col] == board[row + ][col - ]

                         && board[row][col] == board[row + ][col - ] && board[row][col] == board[row + ][col - ]) {

                     return true;

                 }

             }

         }

         return false;

     }

     public char switchPlayer(char currentPlayer) {

         if (currentPlayer == 'X') {

             return 'O';

         } else {

             return 'X';

         }

     }

 }