I am very new to processing, and I have an assignment from my professor- I have to make particles appear from the location of my mouse. Well, I achieved this (see below) but I want to know how to make the particles move now, once I click them into existence.  I intend for them to move and bounce around the screen (once they hit the perimeter). 

What do I have to do to achieve this? 

Thank you!!

2. import traer.physics.*;
3. 
   
4. Particle [] ParticleSystem = new Particle [20];
5. 
   
6. 
   
7. void setup() {
8.   size(600, 600);
9.   background(0);
10.   smooth();
11.   for (int i=0; i<20; i++) {
12.     ParticleSystem[i]= new Particle (mouseX, mouseY);
13.   }
14. }
15. 
    
16. void draw () {
17.   //background(100, 200, 255);
18.   // for (int i=0; i<20; i++) {
19.   //ParticleSystem[i].run();
20. }
21. 
    
22. void mousePressed() {
23.   for (int i=0; i<20; i++) {
24.     ParticleSystem[i].run();
25.   }
26. }
28. class Particle {
29.   float x;
30.   float y;
31.   float speedX=2;
32.   float speedY= 8;
33. 
    
34.   Particle (float _x, float _y) {
35.     x=_x;
36.     y=_y;
37.   }
38. 
    
39.   void run() {
40.     display();
41.     //speed();
42.     // bounce();
43.   }
44.   void display() {
45.     rect(mouseX, mouseY, 20, 20);
46.   }
47. 
    
48. 
    
49.   }

p.s. I'm using the physics library from  http://murderandcreate.com/physics/

I am very new to processing and I have been watching Jose Sanchez's tutorials to help get me up to par. 

I was following his tutorial on vector classes and I keep getting the error, 'cannot find anything named "loc"'

Help?

first tab:

2. import toxi.geom.*;
3. 
   
4. 
   
5. ArrayList ballCollection;
6. 
   
7. void setup () {
8.   size(600, 600);
9.   smooth();
10. 
    
11.   ballCollection=new ArrayList ();
12. 
    
13.   for (int i=0; i<1; i++) {
14.     Vec3D origin = new Vec3D(300,300,0);
15.     Ball myBall = new Ball (origin);
16.     ballCollection.add(myBall);
17.   }
18. }
19. 
    
20. void draw() {
21.   background(0);
22. 
    
23.   for (int i= 0; i < ballCollection.size(); i++) {
24.     Ball mb= (Ball) ballCollection.get(i);
25.     mb.run();
26.   }
27. }

second tab: (where the problem occurs)

2. class Ball {
3.   //global variables
4. 
   
5.   Vec3D loc = new Vec3D (0, 0, 0);
6.   Vec3D speed = new Vec3D (random(-2, 2), random(-2, 2), 0);
7. 
   
8.   //constructor
9.   Ball(Vec3D _loc) {
10.     loc = _loc;
11.   }
12.   //functions
13.   void run() {
14.     //display
15.     display();
16.     //move
17.     move();
18.     //bounce
19.     bounce();
20.    
21.   }
22. }
23. void bounce () {
24.   if (loc.y > height) {  <--- this is what it highlights to give me an error message. 
25.     speed.y= speed.y *-1;
26.   }
27.   if (loc.y < 0) {
28.     speed.y=speed.y *-1;
29.   }
30.   if (loc.x> width) {
31.     speed.x=speed.x*-1;
32.   }
33.   if (loc.x<0) {
34.     speed.x=speed.x*-1;
35.   }
36. }
37. 
    
38. void move() {
39. 
    
40. 
    
41.   loc.addSelf(speed);
42. }
43. 
    
44. void display() {
45.   ellipse(loc.x, loc.y, 20, 20);
46. }

 Thank you for your assistance!