code: private final AbstractItem _getAndAssertItem() throws SevereMessageStoreException
      {
          if (TraceComponent.isAnyTracingEnabled() && tc.isEntryEnabled())
              SibTr.entry(tc, "_getAndAssertItem");
  
          AbstractItem item = null;
          synchronized (this)
          {
              item = _strongReferenceToItem;
          }
  
          // Defect 601995
          if (item == NULL_STRONG_REF)
          {
              if (TraceComponent.isAnyTracingEnabled() && tc.isEntryEnabled())
                  SibTr.exit(tc, "_getAndAssertItem");
              throw new SevereMessageStoreException("_getAndAssertItem");
          }
  
          if (TraceComponent.isAnyTracingEnabled() && tc.isEntryEnabled())
              SibTr.exit(tc, "_getAndAssertItem", item);
          return item;
      }
docs: Gets a reference to the item, which is asserted to be obtained from the
  strong reference. We use this when we know that the state of the item
  tells us that there is a strong reference.
  
  @throws SevereMessageStoreException