private void parseResponse(String response) throws Exception {
    if (response != null) {
        // some code
    }
}

DataTap tap = new DataTap();
Deencapsulation.invoke(tap, "parseResponse", "hello");

// this line throws NPE
Deencapsulation.invoke(tap, "parseResponse", null);

Deencapsulation.invoke(tap, "parseResponse", String.class);

Deencapsulation.invoke(tap, "parseResponse", (Object) null);