Java matrix multiplication question

write a program in java to take a file input.txt with nxn matrix and multiply with another matrix of same dimensions whose all elements are 1.

Ex take A =

1 2 3

4 5 6

7 8 9

2nd matrix

1 3 4

5 7 8

9 10 11

the program should perform the operation for any nxn matrix in input file.