You're overriding the global varible in your setup with float[][] pointsArray, making it local to setup.  The first line in your setup initializes the global pointsArray.  You're second line creates a new local variable pointsArray, which is disposed of at the end of setup().  Your draw calls the global, which is still empty.  You would think that removing float[][] in the setup should fix it, but Processing doesn't like creating a array via {} when you define the array earlier.  So I guess you could do this:

1. float[][] pointsArray = { 
2.   {
3.     0, 1, 2, 3
4.   }
5.   ,
6.   {
7.     3, 2, 1, 0
8.   }
9.   ,
10.   {
11.     3, 5, 6, 1
12.   }
13.   ,
14.   {
15.     3, 8, 3, 4
16.   }
17. };
18. void setup()
19. {
20.   // pointsArray= new float[4][4];
21. }
22. void draw()
23. {
24.   println(pointsArray[1][1]);
25. }

or

1. float[][] pointsArray;
2. void setup()
3. {
4.   pointsArray= new float[4][4];
5.   float[][] pArray = { 
6.     {
7.       0, 1, 2, 3
8.     }
9.     ,
10.     {
11.       3, 2, 1, 0
12.     }
13.     ,
14.     {
15.       3, 5, 6, 1
16.     }
17.     ,
18.     {
19.       3, 8, 3, 4
20.     }
21.   };
22.   pointsArray = pArray;
23. }
24. void draw()
25. {
26.   println(pointsArray[1][1]);
27. }

Tank you it's work !