title: How to convert "Hashmap values of List type" into Set?
body: <p>How to get concatenate "List of values" in a Map to create single list and then to pass into another method:</p>
  
  <pre><code>Map&lt;Long,List&lt;Long&gt;&gt; activities = new HashMap();
  for(Something s: something){
    activities .put(prosessLongID, listOfSubProcesses);
  } //There are 5 something and for each there are 2 List of Subprocesses which makes 10 Subprocesses
  </code></pre>
  
  <p>I want to concatenate list of Subprocesses from above Map to create a Set:</p>
  
  <pre><code> ImmutableSet.copyOf(listOfSubProcesses_ForAllSomething) //com.google.common.collect
  </code></pre>
  
  <p>Is there any method in Map which returns all List of SubProcesses in single list which i could pass in above method?    </p>
  
  <p>Note: I got response from @Eran on Java 8 and thanks for that. But please consider Java 6 and solution other then looping. I have facility of APache Commons and Guava.  :)</p>