thnx i fixed it, i had a typo in my code.
i had:
matrix.set(2, 0, nine);
matrix.set(2, 3, ten);
matrix.set(2, 3, eleven);
matrix.set(2, 3, twelve);
instead of
matrix.set(2, 0, nine);
matrix.set(2, 1, ten);
matrix.set(2, 2, eleven);
matrix.set(2, 3, twelve);