Question

Create a connect four board game in java. Use multiple methods and 2d arrays. The purpose of the game is to get four red "R" or yellow "Y" pucks in a row(vertically,horizontally, or diagonally)

Answer 1

//JAVA PROGRAM FOR CONNECT 4 GAME
import java.util.Arrays;
import java.util.Scanner;
import java.util.stream.Collectors;
import java.util.stream.IntStream;

// we are going to create a simple 2-players Connect Four implementation in Java 8
public class ConnectFour {

// we define characters for players (R for Red, Y for Yellow)
private static final char[] PLAYERS = {'R', 'Y'};
// dimensions for our board
private final int width, height;
// grid for the board
private final char[][] grid;
// we store last move made by a player
private int lastCol = -1, lastTop = -1;

public ConnectFour(int w, int h) {
width = w;
height = h;
grid = new char[h][];

// init the grid will blank cell
for (int i = 0; i < h; i++) {
Arrays.fill(grid[i] = new char[w], '.');
}
}

// we use Streams to make a more concise method
// for representing the board
public String toString() {
return IntStream.range(0, width).
mapToObj(Integer::toString).
collect(Collectors.joining()) +
"\n" +
Arrays.stream(grid).
map(String::new).
collect(Collectors.joining("\n"));
}

// get string representation of the row containing
// the last play of the user
public String horizontal() {
return new String(grid[lastTop]);
}

// get string representation fo the col containing
// the last play of the user
public String vertical() {
StringBuilder sb = new StringBuilder(height);

for (int h = 0; h < height; h++) {
sb.append(grid[h][lastCol]);
}

return sb.toString();
}

// get string representation of the "/" diagonal
// containing the last play of the user
public String slashDiagonal() {
StringBuilder sb = new StringBuilder(height);

for (int h = 0; h < height; h++) {
int w = lastCol + lastTop - h;

if (0 <= w && w < width) {
sb.append(grid[h][w]);
}
}

return sb.toString();
}

// get string representation of the "\"
// diagonal containing the last play of the user
public String backslashDiagonal() {
StringBuilder sb = new StringBuilder(height);

for (int h = 0; h < height; h++) {
int w = lastCol - lastTop + h;

if (0 <= w && w < width) {
sb.append(grid[h][w]);
}
}

return sb.toString();
}

// static method checking if a substring is in str
public static boolean contains(String str, String substring) {
return str.indexOf(substring) >= 0;
}

// now, we create a method checking if last play is a winning play
public boolean isWinningPlay() {
if (lastCol == -1) {
System.err.println("No move has been made yet");
return false;
}

char sym = grid[lastTop][lastCol];
// winning streak with the last play symbol
String streak = String.format("%c%c%c%c", sym, sym, sym, sym);

// check if streak is in row, col,
// diagonal or backslash diagonal
return contains(horizontal(), streak) ||
contains(vertical(), streak) ||
contains(slashDiagonal(), streak) ||
contains(backslashDiagonal(), streak);
}

// prompts the user for a column, repeating until a valid choice is made
public void chooseAndDrop(char symbol, Scanner input) {
do {
System.out.println("\nPlayer " + symbol + " turn: ");
int col = input.nextInt();

// check if column is ok
if (!(0 <= col && col < width)) {
System.out.println("Column must be between 0 and " + (width - 1));
continue;
}

// now we can place the symbol to the first
// available row in the asked column
for (int h = height - 1; h >= 0; h--) {
if (grid[h][col] == '.') {
grid[lastTop = h][lastCol = col] = symbol;
return;
}
}

// if column is full ==> we need to ask for a new input
System.out.println("Column " + col + " is full.");
} while (true);
}

public static void main(String[] args) {
// we assemble all the pieces of the puzzle for
// building our Connect Four Game
try (Scanner input = new Scanner(System.in)) {
// we define some variables for our game like
// dimensions and nb max of moves
int height = 6; int width = 8; int moves = height * width;

// we create the ConnectFour instance
ConnectFour board = new ConnectFour(width, height);

// we explain users how to enter their choices
System.out.println("Use 0-" + (width - 1) + " to choose a column");
// we display initial board
System.out.println(board);

// we iterate until max nb moves be reached
// simple trick to change player turn at each iteration
for (int player = 0; moves-- > 0; player = 1 - player) {
// symbol for current player
char symbol = PLAYERS[player];

// we ask user to choose a column
board.chooseAndDrop(symbol, input);

// we display the board
System.out.println(board);

// we need to check if a player won. If not,
// we continue, otherwise, we display a message
if (board.isWinningPlay()) {
System.out.println("\nPlayer " + symbol + " wins!");
return;
}
}
  
System.out.println("Game over. No winner. Try again!");
}
}

}