Connect Four

import java.util.*;

public class fourClass {

static int ROWS = 6;
static int COLUMNS = 7;

public static void main(String args[]) {
 
// Array
String[][] fourGrid = new String[ROWS][COLUMNS];

// Console
Scanner console    = new Scanner (System.in);

// winner?
boolean noWinner = true;

printHeader ();

// Initialize the Board to 'O'

for (int i = 0; i < fourGrid.length; i++) {
for (int j = 0; j < fourGrid[i].length; j++) {
fourGrid[i][j] = "O";
}
}

printBoard (fourGrid); System.out.println();

while (noWinner) {
if (!isBoardFull(fourGrid)) {
System.out.print ("Player 1 (Red) Turn> ");
String turn = console.nextLine();
System.out.println();
playGame (fourGrid, turn, "R");
} else {
System.out.println("Tie game, you both lose");
System.exit(0);
}

System.out.println();

if (!isBoardFull(fourGrid)) {
System.out.print ("Player 2 (BLACK) Turn> ");
String turn = console.nextLine();
System.out.println();
playGame (fourGrid, turn, "B");
System.out.println();
} else {
System.out.println("Tie game, you both lose");
System.exit(0);
}
}

console.close();
}

/*
* playGame - main part of game used by both Red & Black
*
* parameters: 2D String array, the input from console, whose turn it is
* return: void
*
*/
public static void playGame (String [][] fourGrid, String turn, String coin) {

if (containsComma(turn)) {

String[] turnSplit = turn.split(",");

if (isInteger(turnSplit[0]) && isInteger(turnSplit[1])) {
int row = Integer.parseInt (turnSplit[0]);
int column = Integer.parseInt (turnSplit[1]);

System.out.println ("This is like coding:  grid[" + row + "][" + column + "] = \"" + coin + "\";");
System.out.println();

if ((verifyValid (row, column) == true) &&
(verifyBottom(fourGrid, row, column) == true) &&
(verifyEmpty(fourGrid, row, column) == true)) {

updateGrid(fourGrid, row, column, coin);

if ((checkColumn (fourGrid, row, column, coin) == true) ||
(checkRow (fourGrid, row, column, coin) == true) ||
(checkBackwardsDiagonal (fourGrid, row, column, coin) == true) ||
(checkForwardDiagonal (fourGrid, row, column, coin) == true)) {
printBoard(fourGrid);
System.out.println (coin + " wins but James is still World Champion");
System.exit(0);
}
} else {
System.out.println ("INVALID CHOICE.  LOSS OF TURN");
}
} else {
System.out.println ("INVALID CHOICE.  LOSS OF TURN");
}
} else {
System.out.println ("INVALID CHOICE.  LOSS OF TURN");
}

printBoard(fourGrid);
}

/*
* printHeader - print some instructions
*
* parameters: void
* return: void
*
*/
public static void printHeader () {
System.out.println("Welcome to James Connect Four game");
System.out.println("(true gamers just call it 'four')");
System.out.println();
System.out.println("To play, type in the array element on where you want to play your coin:");
System.out.println("Use the format 2,3 to correspond with [2][3]");
System.out.println();
System.out.println("If you mess up, you lose a turn!");
System.out.println();
System.out.println("Good luck, but remember, I'm still the World Champion");
System.out.println();

}


/*
* printBoard - print the whole board
*
* parameters: 2D String array
* return: void
*
* Go through the grid and print the element and a space after
*/
public static void printBoard (String[][] grid) {
for (int i = 0; i < grid.length; i++) {
for (int j = 0; j < grid[i].length; j++) {
System.out.print (grid[i][j] + " ");
}

System.out.println();
}
}

/*
* isBoardFull - make sure there isn't a tie
*
* parameters: 2D String array
* return: true/false
*
* Go through the grid and make sure there is a "O"
*/
public static boolean isBoardFull (String[][] grid) {
for (int i = 0; i < grid.length; i++) {
for (int j = 0; j < grid[i].length; j++) {
if (grid[i][j].equals("O")) {
return false;
}
}
}

return true;
}

/*
* verifyValid - make sure row & column is in range
*
* parameters: row element, column element
* return: true/false
*
* Go through the grid and make sure there is a "O"
*/
public static boolean verifyValid (int rows, int columns) {
if ((rows >= ROWS) || (columns >= COLUMNS) || (rows < 0) || (columns < 0)) {
return false;
}

return true;
}

/*
* updateGrid - valid play, now update the 2D array
*
* parameters: 2D String array, row position, column position, color of coin
* return: void
*
*/
public static void updateGrid (String[][] grid, int row, int column, String coin) {

grid[row][column] = coin;
}

/*
* verifyBottom - checks to see if there is a coin underneath the position they are
*                playing
*
* parameters: 2D String array, row position, column position
* return: void
*
*/
public static boolean verifyBottom (String[][] grid, int row, int column) {

if (row == 5) {
return true;
} else {
while (row != 5) {
row++;

if (grid[row][column].equals("O")) {
return false;
}
}
}

return true;
}

/*
* verifyEmpty - checks to see if someone already played a coin there
*
* parameters: 2D String array, row position, column position
* return: true/false
*
*/
public static boolean verifyEmpty (String[][] grid, int row, int column) {

if (!grid[row][column].equals("O")) {
return false;
}

return true;
}

/*
* checkRow - checks to see if there is 4 in a row left to right
*
* parameters: 2D String array, row position, column position, color of coin
* return: true/false
*
*/
public static boolean checkRow (String[][] grid, int row, int column, String coin) {

int count = 0;
int original_position = row;

// go down
while ((row < ROWS) && grid[row][column].equals(coin)) {
count++;
row++;
}

//go up.  we already got the original so decrement

row = original_position - 1;

while ((row >= 0) && grid[row][column].equals(coin)) {
count++;
row--;
}

if (count == 4) {
return true;
}

return false;
}

/*
* checkColumn - checks to see if there is 4 in a row up/down
*
* parameters: 2D String array, row position, column position, color of coin
* return: true/false
*
*/
public static boolean checkColumn (String[][] grid, int row, int column, String coin) {
int count = 0;
int original_position = column;

// go down
while ((column < COLUMNS) && grid[row][column].equals(coin)) {
count++;
column++;
}


column = original_position - 1;

while ((column >= 0 && grid[row][column].equals(coin) )) {
count++;
column--;
}

if (count == 4) {
return true;
}

return false;
}

/*
* checkBackwardsDiagonal - checks to see if there is 4 in a row diagonally
*
* parameters: 2D String array, row position, column position, color of coin
* return: true/false
*
*
*  x  0  0
*  0  x  0
*  0  0  x
*/
public static boolean checkBackwardsDiagonal (String[][] grid, int row, int column, String coin) {
int count = 0;
int original_row_position = row;
int original_column_position = column;

while ((column < COLUMNS) && (row < ROWS) && grid[row][column].equals(coin)) {
count++;
column++;
row++;
}

row = original_row_position - 1;
column = original_column_position - 1;

while ((column >= 0) && (row >= 0) && (grid[row][column].equals(coin))) {
count++;
row--;
column--;
}

if (count == 4) {
return true;
}

return false;
}


/*
* checkForwardDiagonal - checks to see if there is 4 in a row diagonally
*
* parameters: 2D String array, row position, column position, color of coin
* return: true/false
*
*
*  0  0  x
*  0  x  0
*  x  0  0
*/
public static boolean checkForwardDiagonal (String[][] grid, int row, int column, String coin) {
int count = 0;
int original_row_position = row;
int original_column_position = column;

while ((column < COLUMNS) && (row >= 0) && grid[row][column].equals(coin)) {
count++;
row--;
column++;
}

row = original_row_position + 1;
column = original_column_position - 1;

while ((column >= 0) && (row < ROWS) && (grid[row][column].equals(coin))) {
count++;
row++;
column--;
}

if (count == 4) {
return true;
}

return false;
}

/*
* isInteger - See if the string is valid number
*
* parameters: String (an element, example: "1")
* return: true/false
*/
public static boolean isInteger (String input) {

// always the first
if (!input.equals(null)) {
char ch = input.charAt(0);

if (!Character.isDigit(ch)) {
return false;
}
} else {
return false;
}

return true;
}

/*
* containsComma - See if the string has ,
*
* parameters: String (ex. "1,2")
* return: true/false
*/
public static boolean containsComma (String input) {
for (int i = 0; i < input.length(); i++) {
char ch = input.charAt(i);

if (ch == ',') {
return true; // found comma
}
}

return (false);
}
}