Libgdx OrthographicCamera - How to set graphical objects always to center?

Newbie & Debugging Questions
#1

I have defined VIEWPORT_WIDTH and VIEWPORT_HEIGHT values. After that I would like to set all my objects to the center of this area. By default I see all of my graphical items, sprites at the left corner. I use now this code:

        camera = new OrthographicCamera(VIEWPORT_WIDTH, VIEWPORT_HEIGHT);
        camera.position.set(camera.viewportWidth/2f, camera.viewportHeight/2f, 0);

It is a complex object(It is from lines and circles), drawed by ShapeRenderer.
How can I set “always center”?

#2

By default the origin of the OrthographicCamera is the center of it’s view. So camera.position.x and camera.position.y would be where to draw your objects that you want centered.

#3

It is not only one object. There have been used two different shapes.