@Override public boolean isValidConfiguration() { boolean isValid = true; long numFinite = vars.getListOfVariables().stream() .filter( v -> v.getStateSpaceTypeEnum().equals(StateSpaceTypeEnum.FINITE_SET)) .count(); if(numFinite <2) { isValid = false; String errorMsg = "Invalid configuration: There should be at least 2 discrete variables (root and class)"; this.setErrorMessage(errorMsg); } return isValid; }