Thread: Need help with Game of Life generations

I'm making a simple game of life 10x10 board using dashes, and filling them in with x's when the user inputs the corresponding row and column. I have everything I need for this except option 3, which is to 'show the next generation' by these rules:
- A new cell is born on an empty square if it is surrounded by exactly three neighbors
- A cell dies of overcrowding if it is surrounded by four or more neighbors
- It dies of loneliness if it is surrounded by zero or one neighbor
- If a cell has two or three neighbors, it survives to the next generation

import java.util.Scanner;
public class GameOfLife
{
    public static void main (String[] args) {
 
        final int ROWS = 10;
        final int COLUMNS = 10;
        Scanner scan = new Scanner(System.in);
        String[][] board = new String[ROWS][COLUMNS];
        for (int i = 0; i < ROWS; i++) 
            for (int j = 0; j < COLUMNS; j++)
                board[i][j] = "-";
 
        boolean done = false;
        while (!done) {
 
            System.out.println("1 - Add a being");
            System.out.println("2 - Show current board");
            System.out.println("3 - Show next generation");
            System.out.println("4 - Clear board");
            System.out.println("5 - Exit");
            int option = scan.nextInt();
 
            if (option == 1) {                
                System.out.print("Enter row for being (1 through 9): ");
                int i = scan.nextInt();
                System.out.print("Enter column for being: ");
                int j = scan.nextInt();
                board[i][j] = "x";        
            }
 
            else if (option == 2) {
                for (int i = 0; i < ROWS; i++) {
                    for (int j = 0; j < COLUMNS; j++)
                        System.out.print(board[i][j]);
                    System.out.println();
                }
            }
 
            else if (option == 3) {
                int neighbors = 0;
                int x = ROWS, y = COLUMNS;                
                if (x >= 1 && y >=1 && x < COLUMNS && y < ROWS) {
                    if (board[x][y++].equals(1)) {neighbors++;}
                    if (board[x][y--].equals(1)) {neighbors++;}
                    if (board[x++][y].equals(1)) {neighbors++;}
                    if (board[x++][y++].equals(1)) {neighbors++;}
                    if (board[x++][y--].equals(1)) {neighbors++;}
                    if (board[x--][y--].equals(1)) {neighbors++;}
                    if (board[x--][y++].equals(1)) {neighbors++;}
                }
 
            }
 
            else if (option == 4) {
                for (int i = 0; i < ROWS; i++)
                    for (int j = 0; j < COLUMNS; j++)
                        board[i][j] = "-";
            }
            else if (option == 5) {
                done = true;
            }
 
            else System.out.println("Invalid input.");            
        }
 
        System.exit(0);
    }
}

I have it so it finds the neighbors but I'm not sure how to go about deleting or keeping certain x's.

For example, how to go from this:

----------
----------
----------
---xxx----
----------
----------
----------
----------
----------
----------

To this:

----------
----------
----x-----
----x-----
----x-----
----------
----------
----------
----------
----------

Originally Posted by Norm

Use the rules of the game to change the contents of a slot depending on what neighbors it has.
Perhaps you need two boards: current and next. Use the current board to set the xs in the next board. Then set current to next.

I have a current board (which is actually just option 2), and I tried just copying that again and using if statements according to the rules, but that's where I'm not sure of how to start it.

Changed my else if for option 3 and now I'm getting this error on the if statements inside of option 3:
java.lang.ArrayIndexOutOfBoundsException: 10

/**
 * Program the mathematical game called The Game of Life.
 * 
 * @author Marcus Stone 
 * @version 11-27-2012
 */
import java.util.Scanner;
public class GameOfLife
{
    public static void main (String[] args) {
        final int ROWS = 10;
        final int COLUMNS = 10;
        Scanner scan = new Scanner(System.in);
        String[][] board = new String[ROWS][COLUMNS];
        String[][] nextGen = new String[ROWS][COLUMNS];
        for (int i = 0; i < ROWS; i++) 
            for (int j = 0; j < COLUMNS; j++)
                board[i][j] = "-";
        boolean done = false;
        while (!done) {
            System.out.println("1 - Add a being");
            System.out.println("2 - Show current board");
            System.out.println("3 - Show next generation");
            System.out.println("4 - Clear board");
            System.out.println("5 - Exit");
            int option = scan.nextInt();
 
            if (option == 1) {                
                System.out.print("Enter row for being (1 through 8): ");
                int i = scan.nextInt();
                System.out.print("Enter column for being (1 through 8): ");
                int j = scan.nextInt();
                board[i][j] = "x";        
            }
            else if (option == 2) {
                for (int i = 0; i < ROWS; i++) {
                    for (int j = 0; j < COLUMNS; j++)
                        System.out.print(board[i][j]);
                    System.out.println();
                }
            }
            else if (option == 3) {
                for (int i = 1; i <= ROWS; i++) {
                    for (int j = 1; j <= COLUMNS; j++) {
                        if (board[i][j] == "x") {
                            int count = 0; {
                                if (board[i][j - 1] == "x")
                                count++;
                                if (board[i][j + 1] == "x")
                                count++;
                                if (board[i - 1][j] == "x")
                                count++;
                                if (board[i - 1][j - 1] == "x")
                                count++;
                                if (board[i - 1][j + 1] == "x")
                                count++;
                                if (board[i + 1][j - 1] == "x")
                                count++;
                                if (board[i + 1][j] == "x")
                                count++;
                                if (board[i + 1][j + 1] == "x")
                                count++;
                            }
                            if (count == 2 || count == 3)
                                board[i][j] = "x";
                            else
                                board[i][j] = "-";
                        }
                        if (board[i][j] == "-") {
                            int nextCount = 0; {
                                if (board[i][j - 1] == "x")
                                nextCount++;
                                if (board[i][j + 1] == "x")
                                nextCount++;
                                if (board[i - 1][j] == "x")
                                nextCount++;
                                if (board[i - 1][j - 1] == "x")
                                nextCount++;
                                if (board[i - 1][j + 1] == "x")
                                nextCount++;
                                if (board[i + 1][j - 1] == "x")
                                nextCount++;
                                if (board[i + 1][j] == "x")
                                nextCount++;
                                if (board[i + 1][j + 1] == "x")
                                nextCount++;
                            }
                            if (nextCount == 3)
                                board[i][j] = "x";
                        }
                        System.out.print(board[i][j]);
                    }
                }
            }
            else if (option == 4) {
                for (int i = 0; i < ROWS; i++)
                    for (int j = 0; j < COLUMNS; j++)
                        board[i][j] = "-";
            }
            else if (option == 5) {
                done = true;
            }
            else System.out.println("Invalid input.");            
        }
        System.exit(0);
    }
}