@Test
    public void confusedAboutJava() throws Exception {
        assertNull(getBody(null));
    }

    public String getBody(DataObject dataObject) {
        return guard(dataObject, DataObject::getData);
    }

    private String guard(DataObject dataObject, Function<DataObject, String> getter) {
        return Optional.ofNullable(dataObject).map(getter).orElse(null);
    }

    static class DataObject {
        private final String data;

        DataObject(String data) {
            this.data = data;
        }

        public String getData() {
            return data;
        }
    }