<function-signature>java.lang.String sdh(java.lang.String)</function-signature>
    <example>${fe:sdh(doc.similar_docs_hash)}</example>
  </function>

  <function>
    <description>Concatenate strings.</description>
    <name>join</name>
    <function-class>org.codelibs.fess.taglib.FessFunctions</function-class>
    <function-signature>java.lang.String join(java.lang.Object)</function-signature>

        ClassTraversalUtil.forEach(con.getJarFile(), (ClassHandler) (packageName, shortClassName) -> {
            if (count < 10) {
                System.out.println(ClassUtil.concatName(packageName, shortClassName));
            }
            assertThat(packageName, is(notNullValue()));
            assertThat(shortClassName, is(notNullValue()));
            assertThat(packageName,

        assertThat(traverser.isExistClass(TestCase.class.getName()), is(not(true)));

        final Set<String> set = new HashSet<String>();
        traverser.forEach((ClassHandler) (packageName, shortClassName) -> set.add(ClassUtil.concatName(packageName, shortClassName)));
        assertThat(set.size() > 0, is(true));
        assertThat(set.contains(DummyTest.class.getName()), is(true));
        assertThat(set.contains(TraverserUtilTest.class.getName()), is(true));

        }

        @Override
        public boolean isExistClass(final String className) {
            final File file = new File(baseDir, toClassFile(ClassUtil.concatName(rootPackage, className)));
            return file.exists();
        }

        @Override
        public void forEach(final ClassHandler handler) {

        for (final File file : dir.listFiles()) {
            final String fileName = file.getName();
            if (file.isDirectory()) {
                traverseFileSystem(file, ClassUtil.concatName(packageName, fileName), handler);
            } else if (fileName.endsWith(".class")) {
                final String shortClassName = fileName.substring(0, fileName.length() - CLASS_SUFFIX.length());

        assertThat(ClassUtil.concatName("aaa", "bbb"), is("aaa.bbb"));
        assertThat(ClassUtil.concatName("aaa", null), is("aaa"));
        assertThat(ClassUtil.concatName("aaa", ""), is("aaa"));
        assertThat(ClassUtil.concatName(null, "bbb"), is("bbb"));
        assertThat(ClassUtil.concatName("", "bbb"), is("bbb"));
        assertThat(ClassUtil.concatName("", "bbb"), is("bbb"));

    }

    /**
     * クラス名の要素を結合します。
     *
     * @param s1
     *            クラス名の要素1
     * @param s2
     *            クラス名の要素2
     * @return 結合された名前
     */
    public static String concatName(final String s1, final String s2) {
        if (StringUtil.isEmpty(s1) && StringUtil.isEmpty(s2)) {
            return null;
        }
        if (!StringUtil.isEmpty(s1) && StringUtil.isEmpty(s2)) {