### Question:
RadixTreeImpl implements RadixTree<T>, Formattable { public T find(String key) { Visitor<T,T> visitor = new VisitorImpl<T,T>() { public void visit(String key, RadixTreeNode<T> parent, RadixTreeNode<T> node) { if (node.isReal()) result = node.getValue(); } }; visit(key, visitor); return visitor.getResult(); } RadixTreeImpl(); T find(String key); boolean delete(String key); void insert(String key, T value); ArrayList<T> searchPrefix(String key, int recordLimit); boolean contains(String key); void visit(String key, Visitor<T, R> visitor); long getSize(); @Deprecated void display(); @Override void formatTo(Formatter formatter, int flags, int width, int precision); String complete(String prefix);  }### Answer:
@Test public void testCantFindRootNode() { assertNull(trie.find("")); }
@Test public void testCantFindNonexistantNode() { assertNull(trie.find("apple")); }