I am sorry to hijack the thread but I think the OP will find the answer to this question useful as well.
Vector2 vec = body.getPosition();
double angle = MathUtils.atan2(vec.y, vec.x);
System.out.println("Angles: " + angle);
I tried this as soon as I saw Riven's answer. It gave me something like 1.1726287603378296 and 0.6320657730102539 as output. There are negative values as well. My question is what the unit of the angle we get here is.
I think it's not an ordinary angle. Because if I get angle by vec.angle() [Libgdx], it is different. This is the output when I add vec.angle() to the system output:
Angles: 0.24124036729335785 or 13.907541