Re: iteration blues
On Nov 3, 4:37 pm, bob <b...@coolgroups.com> wrote:
So, I wrote this code for some particle effects:
package com.coolfone.particles;
import java.util.Iterator;
import java.util.Vector;
import javax.microedition.khronos.opengles.GL10;
public class FireManager {
static Vector<Particle> particles = new Vector<Particle=
();
public static void startfire(float x, float y) {
for (int ctr = 0; ctr < 100; ctr++) {
Particle p = new Partic=
le();
p.x = (float) (x + Math=
..random()-.5);
p.y = (float) (y + Math=
..random()-.5);
p.dx = (float) (Math.ra=
ndom()-.5)/4f;
p.dy = (float) (Math.ra=
ndom()-.5)/4f;
p.timeleft = (int) (Mat=
h.random() * 50 + 50);
particles.add(p);
}
}
public static void burnfire() {
Iterator<Particle> i = particles.iterat=
or();
Vector<Particle> removelist = new Vecto=
r<Particle>();
while (i.hasNext()) {
Particle p = i.next();
p.move();
p.timeleft--;
if (p.timeleft == 0) =
removelist.add(p);
}
particles.removeAll(removelist);
}
public static void drawfire(GL10 gl) {
Iterator<Particle> i = particles.iterat=
or();
while (i.hasNext()) {
Particle p = i.next();
p.draw(gl);
}
}
}
I'm concerned about inefficiency in the burnfire function. Does
anyone know how to rewrite this quickly if particles was a linked
list? The main issue is that I'm not sure if removing items during
iteration messes up the iterator.
all Vectors should be LinkedLists, I think. Since you're only adding
to the end of the list or terating over it, performance shouldn't be
an issue.
BTW, while loops over an iterator are obsolete since Java 1.5 came
out.
Consider using the enhanced for loop:
public static void drawfire(GL10 gl) {
for ( Particle p: particles ) {
p.draw(gl);
}
}
No need to expose the iterator anymore...