code: private Socket evictOldest() {
      Iterator<Entry<SocketAddress, Socket>> iter = 
          multimap.entries().iterator();
      if (!iter.hasNext()) {
        throw new IllegalArgumentException("Cannot evict from empty cache!");
      }
      
      Entry<SocketAddress, Socket> entry = iter.next();
      iter.remove();
      return entry.getValue();
    }
docs: Evict the oldest entry in the cache.