How to throw a parseException in a switch statement?

To increase my projects code coverage, I need to reach the branch ParseException in this method:

public String filterMessage(String actionIn, String messageIn) {
        String message = null;
        try{
            switch (actionIn) {
            //..
            default:
                message = messageIn;
                break;
            }
        }catch (ParseException e) {
            System.out.println("Encountered parse exception");
            e.printStackTrace();
        }catch(IOException ioException){
            ioException.printStackTrace();
        }
        return message;
    }

Instincts are that we must put a String that is "illegal", that can't be parsed because it isn't actually a String, but how do you place something like that without causing a compile error (like putting an int to cause faulse parsing). Any ideas how to test this catch "branch"?