### Question:
DCSeriesNumber { public String toString() { if (series == null) { return (null); } else if (number == null) { return (series); } else { return (series + ";" + number); } } DCSeriesNumber();  DCSeriesNumber(String value);  DCSeriesNumber(String s, String n); String toString(); String getSeries(); String getNumber();  }### Answer:
@Test public void testToString() { dc = new DCSeriesNumber(null, null); assertThat("testToString 0", dc.toString(), nullValue()); dc = new DCSeriesNumber(null, "number"); assertThat("testToString 1", dc.toString(), nullValue()); dc = new DCSeriesNumber("series", null); assertThat("testToString 2", dc.toString(), equalTo("series")); dc = new DCSeriesNumber("series", "number"); assertThat("testToString 3", dc.toString(), equalTo("series;number")); }