there are several examples to start from

e.g. here you could use your 100 letters instead of two balls:
http://www.processing.org/learning/topics/circlecollision.html

or go from here:
http://www.processing.org/learning/basics/arrayobjects.html

1. int unit = 40;
2. int count;
3. Module[] mods;
4. String a1 = "This is a neat program idea I would say! This is a neat program idea I would say! This is a neat program idea I would say! This is a neat program idea I would say!   "+
5. "This is a neat program idea I would say! This is a neat program idea I would say! This is a neat program idea I would say! This is a neat program idea I would say!   ";
6. void setup() {
7.   size(640, 360);
8.   noStroke();
9.   int wideCount = width / unit;
10.   int highCount = height / unit;
11.   count = wideCount * highCount;
12.   mods = new Module[count];
13.   int index = 0;
14.   for (int y = 0; y < highCount; y++) {
15.     for (int x = 0; x < wideCount; x++) {
16.       mods[index++] = new Module(a1.charAt(index)+"", x*unit, y*unit, unit/2, unit/2, random(0.05, 0.8), unit);
17.     }
18.   }
19. }
20. void draw() {
21.   background(0);
22.   for (int i = 0; i < count; i++) {
23.     mods[i].update();
24.     mods[i].draw();
25.   }
26. }
27. class Module {
28.   int xOffset;
29.   int yOffset;
30.   float x, y;
31.   int unit;
32.   int xDirection = 1;
33.   int yDirection = 1;
34.   float speed;
35.   String letter="";
36.   // Contructor
37.   Module(String letterTemp, int xOffsetTemp, int yOffsetTemp, int xTemp, int yTemp, float speedTemp, int tempUnit) {
38.     xOffset = xOffsetTemp;
39.     yOffset = yOffsetTemp;
40.     x = xTemp;
41.     y = yTemp;
42.     speed = speedTemp;
43.     unit = tempUnit;
44.     letter=letterTemp;
45.   }
46.   // Custom method for updating the variables
47.   void update() {
48.     x = x + (speed * xDirection);
49.     if (x >= unit || x <= 0) {
50.       xDirection *= -1;
51.       x = x + (1 * xDirection);
52.       y = y + (1 * yDirection);
53.     }
54.     if (y >= unit || y <= 0) {
55.       yDirection *= -1;
56.       y = y + (1 * yDirection);
57.     }
58.   }
59.   // Custom method for drawing the object
60.   void draw() {
61.     fill(255);
62.     //ellipse(xOffset + x, yOffset + y, 6, 6);
63.     text(letter, xOffset + x, yOffset + y);
64.   }
65. }
66. //

This is great. Thanks. 

yes we need more shuffling and also we need a collision detection and then need a clustering of letters

still lot of work to do.................