I conservatively move this topic to contributed libraries section, although I don't know what JAMA is, and you don't give much clues...

Ok I am sorry not to spend too many words here so I will try to say more. JAMA is a java matrix manipulation package and I searched through Internet in order to find such package and this I think is the best I could find. http://math.nist.gov/javanumerics/jama/

 Also Proccessing has one contributed MatrixMath library - http://matrixmath.fadarch.com/ but I am unsure if it is updated anymore and I would appreciate any advice on its usage...

OK, that's better... People (including me) are often lazy and sometime Google searches can be ambiguous (although, being lazy, I haven't even tried... ). Sometime, people asking questions must make an effort to be answered...

Given the astounding number of answers here, it looks like the first question have been answered...
Now, even if I forgot most of matrix math I learned decades ago, maybe I can help you on the coding side. What have you tried and what errors had you?

This is the main problem...

I have

 Matrix MSHAPE = new Matrix(realMshape); where this realMshape is in fact a double[][] type I got from .txt file. Now only thing is that when I try  etc. MHAPE.times(45) or anything on MSHAPE matrix it throws me NullPointerException. I checked realMshape and it is formated in a way I want, it has 2 columns and 19 rows...

That`s first...thanks a lot

I just tried Jama: downloaded the jar, dragged it on the PDE where I created an empty sketch named JamaTest.
Then I pasted the example given in the doc.:

1. import Jama.*;
2. 
   
3. double[][] vals = {{1.,2.,3},{4.,5.,6.},{7.,8.,10.}};
4. Matrix A = new Matrix(vals);
5. Matrix b = Matrix.random(3,1);
6. Matrix x = A.solve(b);
7. Matrix r = A.times(x).minus(b);
8. double rnorm = r.normInf();
9. 
   
10. A.print(5, 2);
11. b.print(5, 2);
12. x.print(5, 2);
13. r.print(5, 2);

I got some results...
Without your code, I can't help you more.

Well I can send you the executable application if you are willing to look into it. In fact I am starting a specific website dealing with skull shape changes that I seek to model in Processing. I am a biologist in fact and started with Processing couple of months ago. This language is amazing and the thing that biology lacks is for sure clear and understandable visualization that I`m sure Processing can help us with. If you can spare some time you can be my first real collaborator. 

I plan to put it online as soon as finish all the pages (for a week tops).

JAMA sample worked for me too, but I just don`t know why my app does not...