public float getAngle() {
        return FastMath.atan2(y, x);
    }
Returns the angle of the vector in polar coordinates. The current
instance is unaffected.

@return the polar angle in radians, measured counter-clockwise from the
    +X axis (&ge;-Pi, &le;Pi)
jme3-core/src/main/java/com/jme3/math/Vector2f.java