public float angleBetween(Vector2f otherVector) {
        float angle = FastMath.atan2(otherVector.y, otherVector.x)
                - FastMath.atan2(y, x);
        return angle;
    }
Returns the signed angle between the current instance and the argument.
The current instance is unaffected.

@param otherVector the vector to compare (not null, unaffected)
@return the angle in radians, measured counter-clockwise from {@code
    this} to {@code otherVector} (&ge;-2*Pi, &le;2*Pi)
jme3-core/src/main/java/com/jme3/math/Vector2f.java