Merging multiple SVG files into one

first of all I know that there are many similar questions like this, but none of them seem to do the trick for me. I'd like to know if there is any way to combine multiple svg files within one single file. Somewhat like this:

<svg id="background" ...>
   <svg id="first" ...>
       ...
   </svg>
   <svg id="second" ...>
       ...
   </svg>
   ...
</svg>

Is there some sort of template or tutorial that helps me do this? In the end I want to do this programmatically using java und javafx 2.2.