java - I dont get why this code for my Game of Life doesnt work. Can anyone help me? -

the problem when start code game kinda works doesnt behave normal conwys game of life. thought logic section neighbours checked doesnt work should. after long debugging still couldnt find mistake. :)

import java.awt.*;  import javax.swing.*;  public class gui extends jpanel {  private field field; private jframe frame;  public gui() {     int width = 800, height = 800;     frame = new jframe();     frame.setsize(width, height);     frame.setlocationrelativeto(null);     frame.setvisible(true);     frame.add(this);     field = new field(this); }  public static void main(string[] args) {     new gui();  }  public void paint(graphics g) {     super.paint(g);     int j = 0;      (int = 0; < 400; i++) {         j = 0;         (j = 0; j < 400; j++) {             if (field.getalive(i, j)) {                  g.drawrect(2 * j, 2 * i, 2, 2);                 g.fillrect(2 * j, 2 * i, 2, 2);             }         }      }     check();  }  public void check() {     int j = 0;     (int = 1; < 399; i++) {         j = 0;         (j = 1; j < 399; j++) {             if (field.getalive(i, j)) {                  int x = 0;                 if (field.getalive(i - 1, j - 1)) {                     x++;                 }                 if (field.getalive(i, j - 1)) {                     x++;                 }                 if (field.getalive(i + 1, j - 1)) {                     x++;                 }                 if (field.getalive(i + 1, j)) {                     x++;                 }                 if (field.getalive(i - 1, j)) {                     x++;                 }                 if (field.getalive(i - 1, j + 1)) {                     x++;                 }                 if (field.getalive(i, j + 1)) {                     x++;                 }                 if (field.getalive(i + 1, j + 1)) {                     x++;                 }                  if (x < 2 || x > 3) {                     field.setalive(i, j, false);                 }               } else {                   if (!field.getalive(i, j)) {                        int x = 0;                       if (field.getalive(i - 1, j - 1)) {                         x++;                     }                     if (field.getalive(i, j - 1)) {                         x++;                     }                     if (field.getalive(i + 1, j - 1)) {                         x++;                     }                     if (field.getalive(i + 1, j)) {                         x++;                     }                     if (field.getalive(i - 1, j)) {                         x++;                     }                     if (field.getalive(i - 1, j + 1)) {                         x++;                     }                     if (field.getalive(i, j + 1)) {                         x++;                     }                     if (field.getalive(i + 1, j + 1)) {                         x++;                     }                      if (x == 3) {                         field.setalive(i, j, true);                      }                  }             }         }     }     repaint();    }    }       public class field {    private gui gui;    private int fieldlength = 1;    private boolean[][] alive;    public field(gui gui) {     this.gui = gui;     alive = new boolean[400][400];     for(int = 100 ; i<110; i++){alive[100][i] = true;    }     for(int = 100 ; i<110; i++){alive[i][100] = true ;   }   }   public boolean getalive(int i, int j) {     return alive[i][j];   }   public void setalive(int i, int j, boolean alive) {     this.alive[i][j] = alive;   }   } 

your problem caused because using same board instance checking rules , updating. every iteration should create new board based off old 1 instead of re-using old board.

you should maintain 2 boards @ given time. 1 read , 1 write copy written 1 @ end of each iteration