@Test
public void testReverseOrderRandomIntegers() {
Comparator<Integer> naturalOrder = new NaturalOrder<Integer>();
Comparator<Integer> reverse = CollectionUtil.reverseOrder(naturalOrder);
Random random = new Random(243249878l); // Stable "random" sequence
for (int i = 0; i < 65536; i++) {
// Verified to be ~ 50/50 lt/gt
int integer = random.nextInt();
int integerToo = random.nextInt();
assertEquals(0, reverse.compare(integer, integer));
assertEquals(0, reverse.compare(integerToo, integerToo));
int natural = naturalOrder.compare(integer, integerToo);
if (natural == 0) {
// Actually never hits, but eq case is tested above
assertEquals(0, reverse.compare(integer, integerToo));
} else if (natural < 0) {
assertTrue(reverse.compare(integer, integerToo) > 0);
} else {
assertTrue(reverse.compare(integer, integerToo) < 0);
}
}
}
@Test
public void testReverseOrder() {
Comparator<String> naturalOrder = new NaturalOrder<String>();
Comparator<String> reverse = CollectionUtil.reverseOrder(naturalOrder);
assertNotNull(reverse);
assertEquals(0, naturalOrder.compare("foo", "foo"));
assertEquals(0, reverse.compare("foo", "foo"));
assertTrue(naturalOrder.compare("bar", "baz") < 0);
assertTrue(reverse.compare("bar", "baz") > 0);
assertTrue(naturalOrder.compare("baz", "bar") > 0);
assertTrue(reverse.compare("baz", "bar") < 0);
}
@Test(expected = IllegalArgumentException.class)
public void testReverseOrderNull() {
CollectionUtil.reverseOrder(null);
}