ive been making a small program, with a number of Humans, which walk around. When i set the number of Humans a fair amount over 500, the view very clearly pauses with almost regular intervals. I'm not using delay(), noLoop() or something similar and the pauses are not much more frequent with 3000 Humans than with 1000.
ive tried adding small delays, but it merely masks the effect.

Could someone tell me what is causing this?
the code is here: http://www.ai.rug.nl/~dgelling/zombie/infestation.pde

[edit]

one more thing.. is it possible in processing to make two completely different classes in one sketch? such as:

public class one extends applet{
//code here
}

public class two implements actionlistener{
//code here
}

instead of nesting the two?