title: Convert List of List into list in java
body: <pre><code>List&lt;List&lt;String&gt;&gt; superlist = new ArrayList&lt;List&lt;String&gt;&gt;();
  
  List&lt;String&gt; list1 = new ArrayList&lt;String&gt;();
  list1.add("a1");
  list1.add("a2");
  
  List&lt;String&gt; list2 = new ArrayList&lt;String&gt;();
  list2.add("b1");
  list2.add("b2");
  
  List&lt;String&gt; list3= new ArrayList&lt;String&gt;();
  list3.add("c1");
  list3.add("c2");
  
  superlist.add(list1);
  superlist.add(list2);
  superlist.add(list3);
  
  List&lt;String&gt; result= new ArrayList&lt;&gt;();
  </code></pre>
  
  <p>Now I want to create a new list which contains all the values in <code>superList</code>.
  Here result should contain <code>a1,a2,b1,b2,c1,c2</code></p>