### Question:
Pair { public Pair(F first, S second) { this.first = first; this.second = second; } Pair(F first, S second);  Pair(); F getFirst(); void setFirst(F first); S getSecond(); void setSecond(S second);  }### Answer:
@Test public void testPair() { Pair<String, Integer> pair = new Pair<>(); Assert.assertNull(pair.getFirst()); Assert.assertNull(pair.getSecond()); pair.setFirst("Test"); pair.setSecond(5); Assert.assertNotNull(pair.getFirst()); Assert.assertNotNull(pair.getSecond()); Assert.assertEquals("Test", pair.getFirst()); Assert.assertEquals(5, pair.getSecond().intValue()); pair = new Pair<>("foobar", 44); Assert.assertNotNull(pair.getFirst()); Assert.assertNotNull(pair.getSecond()); Assert.assertEquals("foobar", pair.getFirst()); Assert.assertEquals(44, pair.getSecond().intValue()); }