title: Nested flatmap observable rxJava
body: <p>Say I have a blog post api that returns <code>List&lt;Post&gt;</code> which I'd like to translate into something else Using RxJava.  Overall I'd like to break a long string into paragraphs and then words, do something to each word, combine back into paragraphs and combine back into a blog post.  Each  Post can be broken into multiple paragraphs which then could be broken into multiple words. Logically I'd like to do the following and can't find a async manner to do it in.</p>
  
  <ul>
  <li>Create Observable from List</li>
  <li>Split each Observable into <code>Observable&lt;String&gt;</code> on <code>\n</code> which would give me paragraphs</li>
  <li>Split paragraphs into <code>Observable&lt;String&gt;</code> on <code>' '</code> which would segment into words</li>
  <li>Do some kind of transformation to each word (some words will have puncuation as part of them which is fine)</li>
  <li>combine all words back into paragraph putting a space between each one</li>
  <li>combine all paragraphs back into a Post putting a carriage return back between each one.</li>
  </ul>
  
  <p>I'm having trouble figuring out how to do multiple levels of splitting and combining on a particular term.  If I only needed to split into pages I can do something like flatmap(Observable::from).toList() but that won't seem to work.  Any help would be greatly appreciated. </p>