Learning Processing: A Beginner's Guide to Programming Images ...

Example 23-4: Super fancy ArrayList and rectangle particle system
// Declaring a global variable of type ArrayList
ArrayList particles;
// A "Rectangle" will suck up particles
Rectangle blackhole;
void setup() {
size(200,200);
blackhole = new Rectangle(50,150,100,25);
particles = new ArrayList();
smooth();
}
void draw() {
background(255);
// Displaying the Rectangle
stroke(0);
fill(175);
rect(blackhole.x, blackhole.y, blackhole.width,blackhole.height);
// Add a new particle at mouse location
particles.add(new Particle(mouseX,mouseY));
// Loop through all Particles
for (int i = particles.size() – 1; i > = 0; i – – ) {
Particle p = (Particle) particles.get(i);
p.run();
p.gravity();
p.display();
if (blackhole.contains(p.x,p.y)) {
p.stop();
}
if (p.finished()) {
particles.remove(i);
}
}
}
// A simple Particle Class
class Particle {
float x;
float y;
float xspeed;
float yspeed;
float life;
// Make the Particle
Particle(float tempX, float tempY) {
x = tempX;
y = tempY;
xspeed = random(–1,1);
yspeed = random(–2,0);
life = 255;
}
fi g. 23.6
Java 433
If the Rectangle contains the location of the
Particle, stop the Particle from moving.