@Test public void testEmptyIntersection() throws Exception {
		IntervalSet s = IntervalSet.of('a','z');
		IntervalSet s2 = IntervalSet.of('0','9');
		String expecting = "{}";
		String result = (s.and(s2)).toString();
		assertEquals(expecting, result);
	}
Public default constructor used by TestRig
tool-testsuite/test/org/antlr/v4/test/tool/TestIntervalSet.java