code: public void insert(String key, T value) throws DuplicateKeyException {
          try {
  			insert(key, root, value);
  		} catch (DuplicateKeyException e) {
  			// re-throw the exception with 'key' in the message
  			throw new DuplicateKeyException("Duplicate key: '" + key + "'");
  		}
          size++;
      }
docs: /*
  (non-Javadoc)
  @see ds.tree.RadixTree#insert(java.lang.String, java.lang.Object)