docs: public void put(K key, E element) {
          final String methodName = "put(): ";
          stateLock.writeLock().lock();
          try {
              Integer index = actualIndices.remove(key);
              if (index == null)
                  throw new IllegalArgumentException("unknown key: " + key);
              elements[index] = element;
              recordIndex(index);
              checkForCompletion();
              if (tc.isDebugEnabled())
                  Tr.debug(tc, methodName + "element found for key: " + key);
              stateLock.postEvent();
          } finally {
              stateLock.writeLock().unlock();
          }
      }