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