### Question:
XIntervalSeriesCollection extends AbstractIntervalXYDataset implements IntervalXYDataset, PublicCloneable, Serializable { @Override public boolean equals(Object obj) { if (obj == this) { return true; } if (!(obj instanceof XIntervalSeriesCollection)) { return false; } XIntervalSeriesCollection that = (XIntervalSeriesCollection) obj; return ObjectUtils.equal(this.data, that.data); } XIntervalSeriesCollection(); void addSeries(XIntervalSeries series); @Override int getSeriesCount(); XIntervalSeries getSeries(int series); @Override Comparable getSeriesKey(int series); @Override int getItemCount(int series); @Override Number getX(int series, int item); @Override double getStartXValue(int series, int item); @Override double getEndXValue(int series, int item); @Override double getYValue(int series, int item); @Override Number getY(int series, int item); @Override Number getStartX(int series, int item); @Override Number getEndX(int series, int item); @Override Number getStartY(int series, int item); @Override Number getEndY(int series, int item); void removeSeries(int series); void removeSeries(XIntervalSeries series); void removeAllSeries(); @Override boolean equals(Object obj); @Override Object clone();  }### Answer:
@Test public void testEquals() { XIntervalSeriesCollection c1 = new XIntervalSeriesCollection(); XIntervalSeriesCollection c2 = new XIntervalSeriesCollection(); assertEquals(c1, c2); XIntervalSeries s1 = new XIntervalSeries("Series"); s1.add(1.0, 1.1, 1.2, 1.3); c1.addSeries(s1); assertFalse(c1.equals(c2)); XIntervalSeries s2 = new XIntervalSeries("Series"); s2.add(1.0, 1.1, 1.2, 1.3); c2.addSeries(s2); assertEquals(c1, c2); c1.addSeries(new XIntervalSeries("Empty Series")); assertFalse(c1.equals(c2)); c2.addSeries(new XIntervalSeries("Empty Series")); assertEquals(c1, c2); }