code: public void unblockAll()
              throws NoResponseException, XMPPErrorException, NotConnectedException, InterruptedException {
          UnblockContactsIQ unblockContactIQ = new UnblockContactsIQ();
          connection().createStanzaCollectorAndSend(unblockContactIQ).nextResultOrThrow();
      }
docs: Unblock all.
  
  @throws NoResponseException
  @throws XMPPErrorException
  @throws NotConnectedException
  @throws InterruptedException