Yes.

You could for example create xy-coordinates using the noise() or random() functions.

Or you could create a custom particle class that describes movement, display and other behaviors you want.

Yes.

For example:

1. Line line;
2.  
3. void setup()
4. {
5.   size(500, 500);
6.   
7.   line = new Line();
8. }
9.  
10. void draw()
11. {
12.   background(0);
13.   line.update();
14.   line.draw();
15. }
16.  
17. class Line
18. {
19.   float x1, y1;
20.   float x2, y2;
21.  
22.   Line()
23.   {
24.     x1 = width / 3;
25.     y1 = height / 3;
26.     x2 = 2 * width / 3;
27.     y2 = 2 * height / 3;
28.   }
29.   
30.   void update()
31.   {
32.     x1 += random(5)*cos(frameCount/10.0);
33.     y1 -= random(5)*sin(frameCount/10.0);
34.     x2 -= random(5)*cos(frameCount/10.0);
35.     y2 += random(5)*sin(frameCount/10.0);
36.   }
37.  
38.   void draw()
39.   {
40.     stroke(#55FFAA);
41.     strokeWeight(2);
42.     line(x1, y1, x2, y2);
43.   }
44. }