Java Homework

They want me to multiply a matrix using arrays..
So the matrix is an array of arrays?
I'm a bit confused..

if i say
double[][] matrix;
how do i tell which [] has the rows and which has the columns? or is that for me to define?

My name is 9000 and I'm writing a multi-domain interpreted language that will support every language ever inline.

eg:


c {
  include <stdio.h>
}

java {
  String s = "hello world";
  EXPORT_STRING(s);
}

c {
  IMPORT_STRING(&s);
  printf("%s\n",s);
}

ruby {
  IMPORT_STRING(s)
  puts s
}