### Question:
Util { public static int len(Object[] arr) { return empty(arr) ? 0 : arr.length; } private  Util(); static int len(Object[] arr); static int len(Collection collection); static int len(Map map); static int len(String str); static boolean empty(String str); static boolean empty(Object[] arr); static boolean empty(Collection collection); static boolean empty(Map map); static boolean empty(char ch); static void validateKey(Object key); static void validateKey(String key); static String obtainValidKey(Class type); static void validateValue(T value, boolean allowNullValues); static void illegalArg(boolean throwIt, String msg); static void illegalState(boolean throwIt, String msg); static void illegalAccess(boolean throwIt, String msg); static void runtimeException(String msg, Throwable thr); static void notNullArg(Object bob, String msg); static void notNull(Object bob, String msg); static void nonEmptyArg(char ch, String msg); static void nonEmptyArg(String str, String msg); static void nonEmptyArg(Object[] arr, String msg); static void nonEmptyArg(Collection collection, String msg); static void nonEmpty(char ch, String msg); static void nonEmpty(String str, String msg); static void nonEmpty(Object[] arr, String msg); static void nonEmpty(Collection collection, String msg); static void nonEmpty(Map map, String msg); @SuppressWarnings("unchecked") static UncheckedFuture<V> unchecked(Future<V> future); static V getUnchecked(Future<V> future); static void pokeball(Throwable pokemon); static void closeSilently(Closeable closeable); @SuppressWarnings("unchecked") static Class<T> checkedClass(T value); static Future<T> present(T result); static ExecutorService newFixedCachedThread(int threads, ThreadFactory threadFactory); @SuppressWarnings("unchecked") static Cache<K, V> newCacheInstance(Class<? extends Cache> imp, CacheOptions opts);  }### Answer:
@Test public void testLenArray() { assertEquals(0, Util.len((Object[]) null)); assertEquals(0, Util.len(new Object[]{})); assertEquals(1, Util.len(new Object[]{"hello"})); }