Interation between physics objects

what to do, when I want a particular physics object to go through another physics object without any reaction?

But I will interact with them separately then they will react as if they are normal physics object.

But, they will not respond to one another.

Collision groups, read the javadocs of the methods in PhysicsCollisionObject (so all physics objects and controls).

So, just to add only one exception i have to assign all the physics objects to their corresponding certain groups? Is this the way it should be?

Or thinking the other way around, this should be maintained as a good practice, to add physics Objects whenever created should be added , on a certain collision groups?

No, if you set the collisiongroup and the collidewith groups of a physics object to somethng else than the default it will not collide with the rest anymore.