### Question:
ObjectList { public static boolean equals( Object head1, Object head2){ if (head1 != null){ return head1.equals(head2); } else { return head2 == null; } } private  ObjectList(); static Iterator iterator(Object head); static TypedIterator<A> typedIterator(Object head, Class<A> type); static Object createList(Object... values); static Object valueOf(Object o); static Object set(Object head, Object newHead); static Object forceSet(Object head, Object newHead); static Object add(Object head, Object data); static Object replace(Object head, Object oldData, Object newData); static Object remove(Object head, Object data); static boolean contains(Object head, Object o); static boolean containsType(Object head, Class<?> type); static boolean isList(Object head); static boolean isEmpty(Object head); static int size(Object head); static int numberOfInstances(Object head, Class<?> type); static Object get(Object head, int idx); static Object getFirst(Object head); static Object getNext(Object head, Object prevData); static A getFirst(Object head, Class<A> type); static A getNext(Object head, Class<A> type, Object prevData); static void hash(Object head, HashData hd); static boolean equals( Object head1, Object head2); static Object clone(Object head);  }### Answer:
@Test public void testEquals(){ assertTrue( ObjectList.equals(a1, a2)); a1 = null; a2 = "one"; assertFalse( ObjectList.equals(a1, a2)); a1 = "one"; a2 = null; assertFalse( ObjectList.equals(a1, a2)); a1 = ObjectList.createList("one", "two"); a2 = null; assertFalse( ObjectList.equals(a1, a2)); a1 = "one"; a2 = "one"; assertTrue( ObjectList.equals(a1, a2)); a1 = ObjectList.createList("one", "two"); a2 = "one"; assertFalse( ObjectList.equals(a1, a2)); a1 = "one"; a2 = ObjectList.createList("one", "two"); assertFalse( ObjectList.equals(a1, a2)); a1 = ObjectList.createList("one", "two"); a2 = ObjectList.createList("one", "two"); assertTrue( ObjectList.equals(a1, a2)); a1 = ObjectList.createList("one", "two", "three"); a2 = ObjectList.createList("one", "two"); assertFalse( ObjectList.equals(a1, a2)); a1 = ObjectList.createList("one", "two"); a2 = ObjectList.createList("one", "two", "three"); assertFalse( ObjectList.equals(a1, a2)); }