i have a problem and i want u your to suggestions

i have a nXn matrix of any order. i need to make
combinations out of them in such a way that the
combinations should be unique
i am giving u an example
suppose a matrix is like this
A1 B1
A2 B2
the combination generated frm this is
A1 B1
A1 B2
A2 B1
A2 B2
the combinations are unique and the values (A1 A2 B1
B2 )should not repeat with a combination
i need to make a generic algorithm
i am doing this in java and my matrix is String
hoping for a nice reply