public void clear() {
        if (variableList.isEmpty()) {
            return;
        }
        variableMap.clear();
        variableList.clear();
        variablesSet.clear();
        wasModified = true;
    }
Returns true if the given 'newValue' for the given variable 'var' can/should be added without overriding existing info in list
main/src/main/java/cgeo/geocaching/utils/formulas/VariableList.java