Life begins at NullPointerExceptions.???

Question

Hey everybody.
Ok this is a bit hard to explain so here goes.
I am creating the game of life, its a crappy little game that runs at command line, anyway i have coded it all and I tested the methods as i went, all was fine until the last two methods i coded then it all went to $#^!.... The area that is the problem is the counting the array elements around the life form(array element) a 1 = Alive and 0 = dead. The first generation of life works fine but when i create a few generations some index elements return null. Ok i will post my code, it comes in two parts.
If you could take the time to have a look and let me know where im going wrong it would be muchly appreaciated. Cheers.
import  java.io.*;
* The game of life. This is a puzzle style game that automatically creates life
* forms using an MDarray. Life is created depending on other life forms near it.
    public class Life  {
      private static BufferedReader  stdIn = new  BufferedReader(new  InputStreamReader(System.in));
      private static PrintWriter  stdOut = new  PrintWriter(System.out, true);
      private static PrintWriter  stdErr = new  PrintWriter(System.err, true);
      public final static int  ROWS = 8;
      public final static int  COLS = 8;
   /* Number used to determine if alive location born */
      private final static double  BORN = 0.5;
      protected Location[][]  world;
      protected Location[][]  tempCopy;
       public static void  main(String[]  args) throws IOException  {
         int numGens;        
         do     {
            try     {
               stdErr.print("Choose number of Generations:  ");
               stdErr.flush();
               String input = stdIn.readLine();
               numGens = Integer.parseInt(input);
               if (numGens < 1)     {
                  stdErr.println("Number out of range. Please enter a positive integer.");
               else     {
                  break;
                catch      (NumberFormatException nfe)     {
                  stdOut.println("Not a valid number. Please enter a positive integer.");
         while(true);
         Life  ls = new  Life();
         for (int  i = 1; i <= numGens; ++i)  {
            ls.displayWorld(i);
            stdOut.println();
            ls.nextGen();
   * Constructor. Creates the first generation.
       protected Life()  {
         world = new Location[ROWS][COLS];
         tempCopy = new Location[ROWS][COLS];
         for (int i = 0; i < ROWS; i++)     {
            for (int j = 0; j < COLS; j++)     {
               world[i][j] = (Math.random() < BORN) ? Location.ALIVE : Location.NOT_ALIVE;
    * Method creates the first world and populates.
    * @param gen  Integer gen stores the number of the gerneration.
       protected void  displayWorld(int  gen)  {
         stdOut.println("Generation: " + gen);
         for (int i = 0; i < ROWS; i++)     {
            for (int j = 0; j < COLS; j++)     {
               stdOut.print(world[i][j].toString() + " "); //Nullpointer
            stdOut.println();     
    * Method to repopulate the next generation of life forms.
       protected void  nextGen()  {
         for (int i = 1; i < ROWS - 1; i++)     {
            for (int j = 1; j < COLS - 1; j++)     {
               int temp = countNeighbors(i ,j);
               if (!world[i][j].isAlive() && temp == 3){
                  tempCopy[i][j] = Location.ALIVE;
               else if (world[i][j].isAlive() && ((temp <= 1)  || temp > 4 )){
                  tempCopy[i][j] = Location.NOT_ALIVE;
               else if (world[i][j].isAlive() && ((temp > 1) && temp < 4)){
                  tempCopy[i][j] = Location.ALIVE;
         copyNonBorders();
    * This method counts all the areas (array elements) around the life form
    * to decide if there is a life form or not.
    * @param row  Integer row
    * @param col  Integer column
       protected int  countNeighbors(int  row, int  col)  {
            int count = 0;
            if (world[row - 1][col - 1].isAlive())     {
               count++;
            if (world[row - 1][col].isAlive())     {
               count++;
            if (world[row - 1][col + 1].isAlive())     {
               count++;
            if (world[row][col - 1].isAlive())     {
               count++;
            if (world[row][col + 1].isAlive())     { // NullPointer here
               count++;
            if (world[row + 1][col - 1].isAlive())     {
               count++;
            if (world[row + 1][col].isAlive())     {
               count++;
            if (world[row + 1][col + 1].isAlive())     {
               count++;
            return  count;
    * Copies all array elements into a new array excluding the outermost
    * elements. eg Like a border.
       protected void  copyNonBorders()  {
         for (int i = 1; i < ROWS - 1; i++)     {
            for (int j = 1; j < COLS - 1; j++)     {
               world[i][j] = tempCopy[i][j];
   }This is the first part. I have marked the nullpointerexceptions.
I will post the helper class below.

Answer 1

Could it be that you get an ArrayIndexOutOfBounds Exception?
Maybe you should think again about your method to find the number
of neighbors...
private int getNeighbors(int x, int y)
          int nb = 0; // number of neighbors
          // fields above
          if (y != 0)
               if (x != 0)
                    // above left
                    if (map[x - 1][y - 1])
                         nb++;
               // above
               if (map[x][y - 1])
                    nb++;
               if (x != mapsizeArray)
                    // above right
                    if (map[x + 1][y - 1])
                         nb++;
          // fields just left and right
          if (x != 0)
               // left
               if (map[x - 1][y])
                    nb++;
          if (x != mapsizeArray)
               // right
               if (map[x + 1][y])
                    nb++;
          // fields below
          if (y != mapsizeArray)
               // below left
               if (x != 0)
                    if (map[x - 1][y + 1])
                         nb++;
               // below
               if (map[x][y + 1])
                    nb++;
               // below right
               if (x != mapsizeArray)
                    if (map[x + 1][y + 1])
                         nb++;
          return nb;
     }