compiler errors - Java Lang nullpointer exception in animation example? -

import java.awt.*; import javax.swing.imageicon; import javax.swing.jframe; public class images extends jframe {     public static void main(string[] args) {     displaymode dm = new displaymode(800,600,32, displaymode.refresh_rate_unknown);     images = new images();     i.run(dm); }  private screen s; private image bg; private image pic; private boolean nloaded; animation a;      public void run(displaymode dm)     {          nloaded = false;          s = new screen();         try{                  s.setfullscreen(dm, this);                 loadpics();                 movieloop();                 try{                 thread.sleep(50000);                     }catch(exception ex){}         }finally{             s.restorescreen();         }      }      public void movieloop(){         long startingtime = system.currenttimemillis();         long cumtime = startingtime;          while(cumtime-startingtime < 5000)         {             long timepassed = system.currenttimemillis() - cumtime;             cumtime += timepassed;              a.update(timepassed);              graphics g = s.getfullscreenwindow().getgraphics();             draw(g);             g.dispose();              try{             thread.sleep(20);             }catch(exception ex){}          }     }      public void draw(graphics g)     {         g.drawimage(bg, 0,0, null);         g.drawimage(a.getimage(),0,0,null); }       //create load pictures     public void loadpics()     {         bg = new imageicon("c:\\gamepics\\backgroundimage.jpg").getimage();         pic = new imageicon("c:\\gamepics\\smileyicon3.png").getimage();         nloaded = true;         repaint();       }       public void paint(graphics g){         if(g instanceof graphics2d){             graphics2d g2 = (graphics2d)g;             g2.setrenderinghint(renderinghints.key_text_antialiasing, renderinghints.value_text_antialias_on);         }          if(nloaded)         {             g.drawimage(bg, 0, 0, null);             g.drawimage(pic, 300,300, null);         }     }   } 

im not understanding did wrong ive overlooked best can. im practicing simple animation , keep getting 3 null pointer exceptions. ive researched best can , apparently nullpointerexceptions in java have trying size of null arrays? compiler hasn't marked of lists problems im little confused. appreciated. of errors commented out. there 3 of them , in images class

errors:

exception in thread "main" java.lang.nullpointerexception @ images.movieloop(images.java:45) @ images.run(images.java:26) @ images.main(images.java:8) 

animation class

import java.awt.image; import java.util.*; public class animation {  private arraylist scenes; private int sceneindex; private long movietime; private long totaltime; //constructor public animation(){     scenes = new arraylist();     totaltime =0;     start();  } //add scene array list , sets time each scene //for example. if have 3 scenes add t total time 3 times. if had  //3 scenes, 1 1s, 1 2s, 1 3s. total time 6s. , call addscene 3 times public synchronized void addscene(image i, long t) {      totaltime+=t;     scenes.add(new onescene(i, totaltime));  } //start animation beggininign inignngingingnig  public synchronized void start(){ movietime = 0; sceneindex = 0; } //change scenes    //movie time sum of time passed last update //if have more 1 scene. timepassed gets added movietime. //if movietime greater or equal total time(ie. animation complete) restart animation public synchronized void update(long timepassed) {     if(scenes.size() > 1){         movietime += timepassed;         if(movietime >= totaltime)         {             movietime = 0;             sceneindex = 0;          }         while(movietime > getscene(sceneindex).endtime)         {             sceneindex++;         }     } }  public synchronized image getimage(){     if(scenes.size() == 0){         return null;}     else{         return getscene(sceneindex).pic;     } } //getscene private onescene getscene(int x){     return (onescene)scenes.get(x); } //scenes gonna  private class onescene{     image pic;     long endtime;      public onescene(image pic, long endtime)     {         this.pic = pic;                 this.endtime = endtime;      } } } 

i included animation class because compiler highlighting these 3 method calls source of problem

    a.update(timepassed);      movieloop();       i.run(dm);  

please note: long comment

let's start graphics g = s.getfullscreenwindow().getgraphics(); - getgraphics never idea, can return null.

you should never try , update ui component thread other edt , should never draw directly in manner, instead, should using paintcomponent.

you should never dispose of graphics context did not create yourself, prevent other components been painted.

you should avoid overriding paint, of top level container, if no other reason, it's not double buffered (the top level container), , painting on other child components.

check out performing custom painting more details.

you should try using imageio instead of imageicon. imageio throw exceptions if can't read file, imageicon fails silently, no helpful.