code: private void setNonEmptyStringParameter(String key, String value){
          if (value == null){
              parameters.remove(key);
          }
          else if (value.length() == 0){
              throw new IllegalArgumentException("Value cannot be empty.");
          }
          else{
              parameters.put(key, value);
          }
      }
docs: Set a stored parameter and verify it is a non-empty string.
  @param key the parameter's key
  @param value the parameter's value.  Cannot be the empty.  Removes the parameter if null
  string