title: Add Objects from one ArrayList to another
body: <p>I have 9 <code>ArrayList</code>s and I'm trying to condense them all down into one at a given point.</p>
  
  <p>at the moment <code>dotGrid</code> is a matrix of <code>ArrayList</code>s, <code>searchX</code> and <code>searchY</code> simply specify which <code>ArrayList</code>s to add to <code>neighbours</code>.</p>
  
  <pre><code>for(int searchX = sector[0] - 1; searchX &lt; sector[0] + 2; searchX++){
    for(int searchY = sector[1] - 1; searchY &lt; sector[1] + 2; searchY++){
      if(searchX &gt;= 0 &amp;&amp; searchX &lt; 16 &amp;&amp; searchY &gt;= 0 &amp;&amp; searchY &lt; 16){
        neighbours.add(dotGrid[searchX][searchY]);
      }
    }
  }
  </code></pre>
  
  <p>from what I understand <code>neighbours.addAll()</code> should work, but it isn't.</p>
  
  <p>I really have been searching quite hard, but haven't been able to find a satisfactory answer.</p>
  
  <p>thanks in advance</p>