Thread: Pleas help! array index out of bouderies

When I execute my program it gives an error :

java.lang.ArrayIndexOutOfBoundsException: 6
at Field.numNeighbours(GameOfLife.java:131)
at Field.generationNextCalc(GameOfLife.java:164)
at GameOfLife.play(GameOfLife.java:67)
at GameOfLife.main(GameOfLife.java:17)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Nativ e Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknow n Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Un known Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at edu.rice.cs.drjava.model.compiler.JavacCompiler.ru nCommand(JavacCompiler.java:272)

I really don't see it and I hope you can help me.

My code:

import java.util.*;
import java.io.*;
 
class GameOfLife{  // main class
  Field field = new Field();
  Scanner scanner;
  File source;
  String filename = "GameOfLifeInput.txt";
  char[] charArray;
 
  public static void main(String[]args){ // starts up program
    new GameOfLife().play();
  } // end of method
 
  void readInitial(String filename){ // reads input from file
    try{
      source = new File(filename);
      scanner = new Scanner(source);
      String line = null;
      int row = 0;
      int col = 0;
      LineNumberReader lnr = new LineNumberReader(new FileReader(new File(filename)));
      lnr.skip(Long.MAX_VALUE);
      lnr.getLineNumber();
      Cell[][] cells = new Cell[lnr.getLineNumber()][];
 
      while (scanner.hasNext()){
        line = scanner.nextLine();
        char[] charArray = line.toCharArray();
        cells[row] = new Cell[charArray.length];
        for (Character c : charArray){
          Cell cell = new Cell();
          if (c == ' '){
            cell.setAlive(false);
          }else if (c == '*'){
            cell.setAlive(true);
          }
          cells[row][col] = cell;
          ++col;
        }
      ++row;
      col = 0;
      field.setField(cells);
      }
      //field.setField(cells);
    }catch(FileNotFoundException e){
      System.out.println("Could not find or open file due to \n"+e);
    }catch (IOException e) {}
 
  } // end of method 
 
  void play(){ //Asks user for number of generations and execute those generations with brakes of 2 secs in between them
    try{
      int numberOfGenerations = 0;
      int i = 0;
      scanner = new Scanner(System.in);
      System.out.println("How many generations do you want to see?");
      numberOfGenerations = scanner.nextInt();
      readInitial(filename);
      for(i = 0; i < numberOfGenerations; i++){
        field.print();
        field.generationNextCalc();
        Thread.sleep(2000);
      }
    }catch(InterruptedException e){
    }
  }
} // end of class
 
class Field{
  int i, j;
  Cell[][] cells;
 
  void setField(Cell[][] cells){ // method which replaces the empty matrix with the matrix with values read from file
    this.cells = cells;
  }
 
  void drawLine(){ //method to draw lines
    String s = "+";
    for(int i = 1; i < cells[0].length-1; i++){
      s+="--";
    }
    s+="+";
    System.out.println(s);
  } // end of method
 
  public void print(){ //method to print generations
    drawLine();
    for(int i = 1; i < cells.length-1; i++){
      System.out.print("|");
      for(int j = 1; j < cells[i].length-1; j++){
        if(cells[i][j].isAlive()){ 
          System.out.print("*");
        }else{
          System.out.print(" ");
        }
      }
      System.out.println("|");
    }
    drawLine();
 
  } // end of method
 
  int numNeighbours(int i, int j){ // method to count the number of neighbors
    int result = 0;
 
    for(i = 0 ; i<cells[0].length ; i++){
      for(j = 0 ; j<cells.length ; j++){
 
    if(i>0 /*&& j>0 && j<cells.length-1*/){
      if(cells[i-1][j].alive = true){  // Not top and not left and not right
        result++;
      }
    }
    if(i<cells[0].length-1 /*&& j>0 && j<cells.length-1*/){  // Not bottem and not left and not right
      if(cells[i+1][j].alive = true){
        result++;
      }
    }
    if(j>0 /*&& i>0 && i<cells[0].length-1*/){  // Not left and not top and not bottem
      if(cells[i][j-1].alive = true){
        result++;
      }
    }
    if(j<cells.length-1 /*&& i>0 && i<cells[0].length-1*/){  // Not right and not top and not bottem
      if(cells[i][j+1].alive = true){
        result++;
      }
    }
    if(i > 0 && j > 0){  // If cell isn't on the left border and top border
      if(cells[i-1][j-1].alive = true){
        result++;
      }
    }
    if(i > 0 && j < cells.length-1){  // If cell isn't on the right border and top border
      if(cells[i-1][j+1].alive = true){
        result++;
      }
    }
    if(i < cells[0].length-1 && j > 0){  // If cell isn't on the bottem border and not on left border
      if(cells[i+1][j-1].alive = true){
        result++;
      }
    }
    if(i < cells[0].length-1 && j < cells.length-1){  // If the cell isn't on the right border and the bottem border
      if(cells[i+1][j+1].alive = true){
        result++;
      }
    }
      }}
 
    return result;
  } // end of method
 
  void generationNextCalc(){ // method to count the next generation
 
    for (int i = 0; i < cells[0].length-1; i++){
      for (int j = 0; j < cells.length-1; j++){
        int numNeighbours = numNeighbours(i,j);
        if (numNeighbours < 2 || numNeighbours > 3){
          cells[i][j].setAlive(false);
        }else if (numNeighbours == 3){
            cells[i][j].setAlive(true);
        }
      }
    } 
 
    /* (int j = 1; j < cells.length-1; j++){
      for (int i = 1; i < cells[0].length-1; i++){
        cells[i][j] = cells[i][j];
      }
    }*/
  } // end of method
 
} // end of class
 
class Cell{
  boolean alive = false;
  GameOfLife character = new GameOfLife();
 
  boolean isAlive(){
    return alive;   
  } // end of method
 
  void setAlive(boolean state){
    alive = state;
  } // end of method
 
} // end of class

I found the solution of this problem. And I think I have to share this with you. Problem lies here:
for(i = 0 ; i<cells[0].length ; i++){
for(j = 0 ; j<cells.length ; j++){
...........} }
You are accessing "cells[i][j]" array using this two loops. But you have cells array of size cells[cells.length][cells[0].length]. If you get my point you better want to replace above two statements with
for(i = 0 ; i<cells.length ; i++){
for(j = 0 ; j<cells[0].length; j++){
...........} }


Let me know your results.

Thanks,
Ajit