### Question:
KerberosOperationHandler { protected String escapeCharacters(String string, Set<Character> charactersToEscape, Character escapeCharacter) { if (StringUtils.isEmpty(string) || (charactersToEscape == null) || charactersToEscape.isEmpty()) { return string; } else { StringBuilder builder = new StringBuilder(); for (char character : string.toCharArray()) { if (charactersToEscape.contains(character)) { builder.append(escapeCharacter); } builder.append(character); } return builder.toString(); } }  void open(PrincipalKeyCredential administratorCredential, String defaultRealm, Map<String, String> kerberosConfiguration); void close(); abstract boolean principalExists(String principal, boolean service); abstract Integer createPrincipal(String principal, String password, boolean service); abstract Integer setPrincipalPassword(String principal, String password, boolean service); abstract boolean removePrincipal(String principal, boolean service); boolean testAdministratorCredentials(); boolean createKeytabFile(Keytab keytab, File destinationKeytabFile); PrincipalKeyCredential getAdministratorCredential(); void setAdministratorCredential(PrincipalKeyCredential administratorCredential); String getDefaultRealm(); void setDefaultRealm(String defaultRealm); Set<EncryptionType> getKeyEncryptionTypes(); void setKeyEncryptionTypes(Set<EncryptionType> keyEncryptionTypes); String[] getExecutableSearchPaths(); void setExecutableSearchPaths(String[] executableSearchPaths); void setExecutableSearchPaths(String delimitedExecutableSearchPaths); boolean isOpen(); void setOpen(boolean open); final static String KERBEROS_ENV_LDAP_URL; final static String KERBEROS_ENV_PRINCIPAL_CONTAINER_DN; final static String KERBEROS_ENV_USER_PRINCIPAL_GROUP; final static String KERBEROS_ENV_AD_CREATE_ATTRIBUTES_TEMPLATE; final static String KERBEROS_ENV_KDC_CREATE_ATTRIBUTES; final static String KERBEROS_ENV_ENCRYPTION_TYPES; final static String KERBEROS_ENV_KDC_HOSTS; final static String KERBEROS_ENV_ADMIN_SERVER_HOST; final static String KERBEROS_ENV_KADMIN_PRINCIPAL_NAME; final static String KERBEROS_ENV_EXECUTABLE_SEARCH_PATHS; }### Answer:
@Test public void testEscapeCharacters() throws KerberosOperationException { KerberosOperationHandler handler = createHandler(); HashSet<Character> specialCharacters = new HashSet<Character>() { { add('/'); add(','); add('\\'); add('#'); add('+'); add('<'); add('>'); add(';'); add('"'); add('='); add(' '); } }; Assert.assertEquals("\\/\\,\\\\\\#\\+\\<\\>\\;\\\"\\=\\ ", handler.escapeCharacters("/,\\#+<>;\"= ", specialCharacters, '\\')); Assert.assertNull(handler.escapeCharacters(null, specialCharacters, '\\')); Assert.assertEquals("", handler.escapeCharacters("", specialCharacters, '\\')); Assert.assertEquals("nothing_special_here", handler.escapeCharacters("nothing_special_here", specialCharacters, '\\')); Assert.assertEquals("\\/\\,\\\\\\#\\+\\<\\>\\;\\\"\\=\\ ", handler.escapeCharacters("/,\\#+<>;\"= ", specialCharacters, '\\')); Assert.assertEquals("nothing<>special#here!", handler.escapeCharacters("nothing<>special#here!", null, '\\')); Assert.assertEquals("nothing<>special#here!", handler.escapeCharacters("nothing<>special#here!", Collections.emptySet(), '\\')); Assert.assertEquals("nothing<>special#here!", handler.escapeCharacters("nothing<>special#here!", Collections.singleton('?'), '\\')); Assert.assertEquals("\\A's are special!", handler.escapeCharacters("A's are special!", Collections.singleton('A'), '\\')); }