### Question:
DefaultMultiValueCategoryDataset extends AbstractDataset implements MultiValueCategoryDataset, RangeInfo, PublicCloneable { @Override public int getRowCount() { return this.data.getRowCount(); } DefaultMultiValueCategoryDataset(); void add(List<Number> values, Comparable rowKey, Comparable columnKey); @Override List<Number> getValues(int row, int column); @Override List<Number> getValues(Comparable rowKey, Comparable columnKey); @Override Number getValue(Comparable row, Comparable column); @Override Number getValue(int row, int column); @Override int getColumnIndex(Comparable key); @Override Comparable getColumnKey(int column); @Override List<Comparable> getColumnKeys(); @Override int getRowIndex(Comparable key); @Override Comparable getRowKey(int row); @Override List<Comparable> getRowKeys(); @Override int getRowCount(); @Override int getColumnCount(); @Override double getRangeLowerBound(boolean includeInterval); @Override double getRangeUpperBound(boolean includeInterval); @Override Range getRangeBounds(boolean includeInterval); @Override boolean equals(Object obj); @Override Object clone();  }### Answer:
@Test public void testGetRowCount() { DefaultMultiValueCategoryDataset d = new DefaultMultiValueCategoryDataset(); assertSame(d.getRowCount(), 0); List values = new ArrayList(); d.add(values, "R1", "C1"); assertSame(d.getRowCount(), 1); d.add(values, "R2", "C1"); assertSame(d.getRowCount(), 2); d.add(values, "R2", "C1"); assertSame(d.getRowCount(), 2); }