title: issue with hashmap getting concurrent modification exception
body: <p>I am getting the below error while using map and performing some remove.How to avoid this ?</p>
  
  <pre><code>Caused by: java.util.ConcurrentModificationException
      at java.util.HashMap$HashIterator.nextEntry(HashMap.java:793)
      at java.util.HashMap$EntryIterator.next(HashMap.java:834)
      at java.util.HashMap$EntryIterator.next(HashMap.java:832)
  </code></pre>
  
  <p><BR></p>
  
  <pre><code>   Map&lt;FormField, Object&gt; ItemMap = domainItem.getValues();         
     for (Map.Entry&lt;FormField, Object&gt; ValMap : ItemMap.entrySet()) {         
         List&lt;Field&gt; groupIdList = Mapper.getGroupId(groupFieldId);           
         for (Field field : groupIdList) {
             ItemMap.put(new FormField(field), domainItem.getDomainItemLinkId());
         }
         ItemMap.remove(ValMap.getKey());
     }
  </code></pre>