Java: Generator of true's & false's combinations by giving the number N;

Question

I tied to simplify the task as much as possible, so I could apply it to my algorithm.

And here is the challenge for mathematicians and programmers:

I need to

Answer 1

This should do the trick

int cols = 3;
int rows = (int) Math.pow(2, cols);
for (int row = 0; row < rows; row++)
    System.out.println(String.format("%" + cols + "s", 
            Integer.toBinaryString(row)).replace(' ', '0').replace('1', 'X'));

out:

000
00X
0X0
0XX
X00
X0X
XX0
XXX