title: How to do add all with java streams?
body: <p>How do I do add all with java 8 ?</p>
  
  <pre><code>processeditemList is a Map&lt;Integer, Map&lt;Item, Boolean&gt;&gt; 
  </code></pre>
  
  <p>As for now I am doing :</p>
  
  <pre><code>List&lt;Item&gt; itemList = Lists.newLinkedList();
  for (Map&lt;Item, Boolean&gt; entry : processeditemList.values()) {
      itemList.addAll(entry.keySet());
  }
  return itemList;
  </code></pre>