title: rxjava collect objects by condition and wait for another observable
body: <p><a href="http://i.stack.imgur.com/RrgTf.png" rel="nofollow">Need process</a>
  I have 2 observables that can produce orange and green objects (1 and 2). This two objects a pair (green activate orange by timer other trigger).</p>
  
  <p>Some time I have situation when different observables can emit (produce) same orange objects (A and B same inside). In such situation I need check if A equals B and left one object to wait for green activator (A and B, of course, could be different). If will come green activator for A or B, I need check if green activator fit for orange, and do actions.</p>
  
  <p>I think I should use PublishObjects and combine green and orange objects (do not not how to check condition and left object if it do not fit) and even have no guess how to combine 2 orange objects together. Pls any guess how to it?</p>