Any help with this program (a bit of a problem with static references)

Question

Can anyone give me any suggestions for fixing this code:
package vivarium;
import javax.swing.JApplet;
import javax.swing.JFrame;
import java.awt.*;
import java.applet.*;
import java.net.*;
public class Render extends java.applet.Applet {
     static Animal[] animal_array_world;
     public static void main(String s[])  {
          JFrame frame = null;
          Graphics g = null;
          int[][] grassarray = new int[16][16];
          createapplet(frame);
          Render r = new Render();
          r.rendergrass(g, grassarray);
          frame.paint(g);
          //createcreatures(20);
          //live();
     public void rendergrass(Graphics g, int[][] array) {
          URL codebase = getCodeBase();
          java.awt.Image grass =  getImage(codebase, "grass.JPG");
          java.awt.Image deadgrass =  getImage(codebase, "deadgrass.JPG");
          for(int i = 0; i < 16; i++)
               for(int j = 0; j < 16; j++) {
                    int y = (i * 16);
                    int x = (j * 16);
               if(array[i][j] == 0) {
                    drawimage(g, grass, y, x);
               else
                    drawimage(g, deadgrass, y, x);
     public  void drawimage(Graphics g, java.awt.Image img, int y, int x) {
          g.drawImage(img, y, x, this);
     public static void createapplet(JFrame frame) {
          frame = new JFrame();
          frame.setTitle("Kirby's Vivarium Demo");
          frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
          JApplet applet = new RenderApplet();
          applet.init();
          frame.getContentPane().add(applet);
          frame.pack();
          frame.setVisible(true);
     //this creates an array of creatures
     public static void createcreatures(int x) {
          animal_array_world = new Animal[x*2];
     //this will than act on that
     public static void live() {
          while(true) {
          int i = 0;
          while(i != animal_array_world.length - 1) {
               animal_array_world.live(animal_array_world);
The problem seems to be with
URL codebase = getCodeBase();
java.awt.Image grass =  getImage(codebase, "grass.JPG");
java.awt.Image deadgrass =  getImage(codebase, but I do not get how. This is a non-static field, but no matter what I do it seems to complain in some manner. Does anyone have any suggestions? Thanks!

Answer 1

Exception in thread "main" java.lang.NullPointerException
     at java.applet.Applet.getCodeBase(Unknown Source)
     at vivarium.Render.rendergrass(Render.java:29)
     at vivarium.Render.main(Render.java:20)I get this despite whether I put the getCodeBase part in a method, the main or the initialization block.
Heres line 29: URL codebase = getCodeBase();This is called within my nonstatic method rendergrass.
And heres line 20: r.rendergrass(g, grassarray);(Where r is a new Render class object)