Re-adding Topics to SVN

java/examples/Topics/Simulate/MultipleParticleSystems/ParticleSystem.pde

@@ -0,0 +1,51 @@
+// An ArrayList is used to manage the list of Particles 
+
+class ParticleSystem {
+
+  ArrayList particles;    // An arraylist for all the particles
+  PVector origin;        // An origin point for where particles are birthed
+
+  ParticleSystem(int num, PVector v) {
+    particles = new ArrayList();              // Initialize the arraylist
+    origin = v.get();                        // Store the origin point
+    for (int i = 0; i < num; i++) {
+      // We have a 50% chance of adding each kind of particle
+      if (random(1) < 0.5) {
+        particles.add(new CrazyParticle(origin)); 
+      } else {
+        particles.add(new Particle(origin)); 
+      }
+    }
+  }
+
+  void run() {
+    // Cycle through the ArrayList backwards b/c we are deleting
+    for (int i = particles.size()-1; i >= 0; i--) {
+      Particle p = (Particle) particles.get(i);
+      p.run();
+      if (p.dead()) {
+        particles.remove(i);
+      }
+    }
+  }
+
+  void addParticle() {
+    particles.add(new Particle(origin));
+  }
+
+  void addParticle(Particle p) {
+    particles.add(p);
+  }
+
+  // A method to test if the particle system still has particles
+  boolean dead() {
+    if (particles.isEmpty()) {
+      return true;
+    } 
+    else {
+      return false;
+    }
+  }
+
+}
+