### Question:
Items { @SuppressWarnings("unchecked") public static <T> T choose(Collection<T> items, SourceOfRandomness random) { int size = items.size(); if (size == 0) { throw new IllegalArgumentException( "Collection is empty, can't pick an element from it"); } if (items instanceof RandomAccess && items instanceof List<?>) { List<T> list = (List<T>) items; return size == 1 ? list.get(0) : list.get(random.nextInt(size)); } if (size == 1) { return items.iterator().next(); } Object[] array = items.toArray(new Object[0]); return (T) array[random.nextInt(array.length)]; } private  Items(); @SuppressWarnings("unchecked") static T choose(Collection<T> items, SourceOfRandomness random); static T chooseWeighted(
        Collection<Weighted<T>> items,
        SourceOfRandomness random);  }### Answer:
@Test public void choosingFromEmptyCollection() { thrown.expect(IllegalArgumentException.class); Items.choose(emptyList(), random); }
@Test public void choosingFromSet() { Set<String> names = new LinkedHashSet<>(asList("alpha", "bravo", "charlie", "delta")); when(random.nextInt(names.size())).thenReturn(2); assertEquals("charlie", Items.choose(names, random)); }