### Question:
RadixTree { public String getLongestPrefix(String path) { RadixNode<T> n = root; Path p = Paths.get(path); int level = 0; while (level < p.getNameCount()) { HashMap<String, RadixNode> children = n.getChildren(); if (children.isEmpty()) { break; } String component = p.getName(level).toString(); if (children.containsKey(component)) { n = children.get(component); level++; } else { break; } } if (level >= 1) { Path longestMatch = Paths.get(root.getName()).resolve(p.subpath(0, level)); String ret = longestMatch.toString(); return path.endsWith("/") ? ret + "/" : ret; } else { return root.getName(); } } RadixTree(); boolean isEmpty(); void insert(String path); void insert(String path, T val); RadixNode<T> getLastNodeInPrefixPath(String path); void removePrefixPath(String path); List<RadixNode<T>> getLongestPrefixPath(String path); @VisibleForTesting /** * Convert radix path to string format for output. * @param path - radix path represented by list of radix nodes. * @return radix path as string separated by "/". * Note: the path will always be normalized with and ending "/". */ static String radixPathToString(List<RadixNode<Integer>> path); String getLongestPrefix(String path);  }### Answer:
@Test public void testGetLongestPrefix() { assertEquals("/a/b/c", ROOT.getLongestPrefix("/a/b/c")); assertEquals("/a/b", ROOT.getLongestPrefix("/a/b")); assertEquals("/a", ROOT.getLongestPrefix("/a")); assertEquals("/a/b/e/g", ROOT.getLongestPrefix("/a/b/e/g/h")); assertEquals("/", ROOT.getLongestPrefix("/d/b/c")); assertEquals("/a/b/e", ROOT.getLongestPrefix("/a/b/e/dir3")); assertEquals("/a/b/c/d", ROOT.getLongestPrefix("/a/b/c/d/p")); assertEquals("/a/b/c/f", ROOT.getLongestPrefix("/a/b/c/f/p")); }