PathHelper { public static String getExtension(final String path) { final int i = path.lastIndexOf('.'); final int j = path.lastIndexOf('/'); if (i == -1 || j > i) return null; return path.substring(i + 1); } private  PathHelper(); static boolean isValid(final String path); static boolean isRelative(final String path); static String getParent(final String path); static String getFileName(final String path); static String getExtension(final String path); static String removeExtension(final String path); static String replaceExtension(final String path, String extension); static String toAbsolute(String dirName, String path); static String fullyQualifiedNameToDirName(
      final String fullyQualifiedName); static String packageNameToDirName(final String packageName); static String fullyQualifiedNameToAbsolute(
      final String fullyQualifiedName, final String path); static String packageNameToAbsolute(final String packageName,
      final String path); static String fullyQualifiedNameToPath(
      final String fullyQualifiedName, final String extension); static String fullyQualifiedNameToPath(
      final String fullyQualifiedName, final String suffix,
      final String extension); static final String PATH_REGEXP; }
@Test(groups = {"functional"}) public void testGetExtension() { assertEquals("txt", getExtension("bar.txt")); assertEquals("txt", getExtension("./bar.txt")); assertEquals("txt", getExtension("foo/bar.txt")); assertEquals("txt", getExtension("./foo/bar.txt")); assertEquals("txt", getExtension("./../foo/bar.txt")); assertNull(getExtension("bar")); assertNull(getExtension("foo.1/bar")); }