How to get a single angle of a spatial

How would one get a single angle, for instance the angle around the y axis that the spatial has.
I tried to use
I thought that that would give me an angle of the Y axis, but it gives me a Vector3f.
Please could you explain why and how I might find the rotation around a single axis?[])

Thank you so much!

In case it helps others:
angles = spatial.getLocalRotation().toAngles(angles);
Quaternion blah = new Quaternion().fromAngles(angles[0], angles[1], angles[2]);