I am fairly new at processing and I have run into a error that I cannot figure out.  I have done some java before, and I don't think that this error would have happened in pure java.

By the way the code is a zombie/human simulation mod that is basically copied off: http://zombies.insertdisc.com/zombies.java by Kevan Davis.  I am just recoding it as an exercise and since I have run into this error my code has been getting closer to Davis's because I am trying to ween out the bug.  Here is my code:

//Containers
Being [] beings;

//Controlling Vars
int numZombies = 1;
int numHumans = 6000;
int totalBeings;

color zombie = color(0,255,0);
color human = color(255,0,0);
color panicHuman = color(255,0,255);
color wall = color(0,0,0);
color nothing = color(1,1,1);

void setup() {
 size(200,200);
 background(0);
 frameRate(30);
 
 totalBeings = numZombies + numHumans;
 
 beings = new Being[totalBeings];

 //Create Zombies
 for(int i = 0; i<numZombies; i++) {
   beings[i] = new Being(true); //True = isZombie
 }
 
 //Create Humans
 for(int i = numZombies; i<totalBeings; i++) {
   beings[i] = new Being(false);
 }
}

void draw() {
 background(0);
 //println(frameRate);
 for(int i = 0;i<totalBeings;i++) {
   beings[i].exist();
 }
}

color look(int x, int y, int dir, int d) {
   int xpos = x;
   int ypos = y;
   for(int i = 0; i < d; i++) {
     if(dir==1) ypos--;
     if(dir==2) xpos++;
     if(dir==3) ypos++;
     if(dir==4) xpos--;

     if(xpos>width-1 || xpos<1 || ypos>height-1 || ypos<1) return wall;
     else if(get(xpos,ypos) == human) return human;
     else if(get(xpos,ypos) == panicHuman) return panicHuman;
     else if(get(xpos,ypos) == zombie) return zombie;
   }
   return nothing;
 }

class Being {

 //State
 boolean isZombie;
 int x,y;
 int dir; //1 = up, 2 = right, 3 = down, 4 = left
 int panic = 0;

 //Controlling vars
 color zombie = color(0,255,0);
 color human = color(255,0,0);
 color panicHuman = color(255,0,255);
 color wall = color(0,0,0);
 color nothing = color(1,1,1);

 int panicTurns = 5;
 int mass = 5;
 int distance = 10;


 Being(boolean isZombie) {
   this.isZombie = isZombie;

   x = (int)random(width)+1;
   y = (int)random(height)+1;
   dir = (int)random(4) + 1;
 }

 //The main loop for the zombie/human.
 void exist() {
   checkState();
   updatePosition();
   apply();
 }

 //This function updates the being's state vars depending on if the being is a zombie or a human
 void checkState() {
   if(isZombie) {
     fill(zombie);
     stroke(zombie);
   }
   else if(panic > 0) {
     fill(panicHuman);
     stroke(panicHuman);
   }
   else {
     fill(human);
     stroke(human);
   }
 }

 void updatePosition() {

   int r = (int)random(10);
   if((!isZombie && panic>0) || r < 3) {
     //update position
     if(look(x,y,dir,1)==nothing) {
       if(dir==1) y--;
       else if(dir==2) x++;
       else if(dir==3) y++;
       else if(dir==4) x--;
     }
     else {
       dir = (int)random(4)+1;
     }

     if(panic>0) panic--;
   }

   int target = look(x,y,dir,distance);

   if(isZombie) {
     //Look around!
     if(target == zombie || target == wall || (target == nothing && (int)random(5) == 1)) {
       dir = (int)random(4)+1;
     }

     int ix = x, iy = y;
     if(dir==1) iy--;
     if(dir==2) ix++;
     if(dir==3) iy++;
     if(dir==4) ix--;
     
     if(target == panicHuman || target == human) println("i see human!");
     
     //Infect something?!
     if(look(x,y,dir,1) == human) { //This line triggers the error
       for(int i=0; i<totalBeings; i++) {
         beings[i].infect(ix,iy);
       }
     }

   } else { //Is I human?!

     //Oh Noes!  Look for zombies!
     if(target == zombie) panic = panicTurns;
     else if(target == wall || target == human) dir = (int)random(4)+1;
     else if(target == nothing && (int)random(8) == 1) dir = (int)random(4)+1;

     //Run away!
     if(target == zombie) {
       dir += 2;
       if(dir>4) dir -= 4;
     }
   }
 }

 void infect(int ix, int iy) {
   if(x == ix && y == iy) isZombie = true;
 }

 void apply() {
   //ellipse(x,y,5,5);
   point(x,y);
 }
}


The error isn't a syntax error or a error processing tells me...  Its just that whenever the if statement that has the error comment (in the updatePosition() function) is uncommented (as it is now), the zombies dont even see humans...  However when it is commented they see humans and infect them.  I am completely lost as to why, because it seems to me that this is just a simple if statement.

Thanks in advance for help!!

On second thought, I see some advantages of using the display memory as state storage: it is updated automatically (when drawing), it doesn't use extra storage, and in our case, it allows partial seeing if being is bigger than one pixel.
And I remembered a simple way to have a copy of this storage, with extra advantage: looking up the copy is faster than using get(). The loadPixels() function will copy the screen display to an array of pixels[]. We can do that just before clearing the background, and we are done.

Update at http://pastebin.com/f385545e

Ah the zombie simulation. That's what initially got me into processing many many years ago.

I made a few variations on it myself:

http://www.hardcorepawn.com/zombie/

http://www.hardcorepawn.com/zombie2/

http://www.hardcorepawn.com/zombie3/ etc..

Ha ha.

I must show the boss Winter Zombies. He will be very upset that someone has already made the zombie city game.

Ok so I hacked this around for a bit and here is what I have come up with.

Zombies increase in size when they kill
Zombies become cannibals (eat other zombies) if they can't find humans and they are about to die
Zombies are much more dangerous

Panic humans make other humans panic

Just play with the variables in the first part of the program and have some fun.  Its really interesting doing extremes like 1 zombie/1000 humans or 0 humans/1000 zombies.  Also experiment with the size of the window as it has a big effect on the zombies winning (killing all humans)...

http://2dsquid.pastebin.com/f52b9750e

 Hack it and see what you can come up with!