How to do unit test for Exceptions?

As you know, exception is thrown at the condition of abnormal scenarios. So how to analog these exceptions? I feel it is challenge. For such code snippets:

public String getServerName() {
    try {

        InetAddress addr = InetAddress.getLocalHost();
        String hostname = addr.getHostName();
        return hostname;
    }
    catch (Exception e) {
        e.printStackTrace();
        return "";
    }
}

Does anybody have good ideas?