title: Add new objects in arraylist to the other arraylist while the second one do not have these new objects
body: <p>If I have two <code>ArrayList</code> one for <code>currentScanWifiList&lt;Router&gt;</code>
  this contains the current wifi scan Routers data 
  and the the second have the same type <code>allUniqueRoutersList&lt;Router&gt;</code>
  used to add the new routers existing in <code>currentScanWifiList</code> and do not exist in allUniqueRoutersList
  the comparing between the routers through equaling its bssid </p>
  
  <pre><code>
  public class Router {
      private String bssid;//identifier
      private String ssid;
      private double x;
      private double y;
      private double meanRss;
  setter and getter....
  }
      for (int x = 0; x &lt; currentScanList.size(); x++) {
          Router currentTempRouter = currentScanList.get(x);
          for (int y = 0; y &lt; allUniqueRoutersList.size(); y++) {
              Router allTempRouter = currentScanList.get(y);
              if (!currentTempRouter.getBssid().equals(allTempRouter.getBssid())) {
                  allUniqueRoutersList.add(currentScanList.get(x));
                  break;
              } 
          }
      }
  </code></pre>
  
  <p>I tried this code but it is not working, it add all objects to <code>allUniqueRoutersList</code>
  not the new ones only 
  what should I do to compare between the two arraylist elements using bssid</p>