Is there any way to detect an RTL language in Java?

ComponentOrientation.getOrientation(new Locale(System.getProperty("user.language"))).isLeftToRight();  

• Resource

I felt a bit dirty relying on AWT classes which are quite dated and I was dealing with BCP-47 language codes, so I ended up copying this code from Google Closure Templates:

/**
 * A regular expression for matching right-to-left language codes.
 * See {@link #isRtlLanguage} for the design.
 */
private static final Pattern RtlLocalesRe = Pattern.compile(
    "^(ar|dv|he|iw|fa|nqo|ps|sd|ug|ur|yi|.*[-_](Arab|Hebr|Thaa|Nkoo|Tfng))" +
    "(?!.*[-_](Latn|Cyrl)($|-|_))($|-|_)");
/**
 * Check if a BCP 47 / III language code indicates an RTL language, i.e. either:
 * - a language code explicitly specifying one of the right-to-left scripts,
 *   e.g. "az-Arab", or<p>
 * - a language code specifying one of the languages normally written in a
 *   right-to-left script, e.g. "fa" (Farsi), except ones explicitly specifying
 *   Latin or Cyrillic script (which are the usual LTR alternatives).<p>
 * The list of right-to-left scripts appears in the 100-199 range in
 * http://www.unicode.org/iso15924/iso15924-num.html, of which Arabic and
 * Hebrew are by far the most widely used. We also recognize Thaana, N'Ko, and
 * Tifinagh, which also have significant modern usage. The rest (Syriac,
 * Samaritan, Mandaic, etc.) seem to have extremely limited or no modern usage
 * and are not recognized.
 * The languages usually written in a right-to-left script are taken as those
 * with Suppress-Script: Hebr|Arab|Thaa|Nkoo|Tfng  in
 * http://www.iana.org/assignments/language-subtag-registry,
 * as well as Sindhi (sd) and Uyghur (ug).
 * The presence of other subtags of the language code, e.g. regions like EG
 * (Egypt), is ignored.
 */
public static boolean isRtlLanguage(String languageString) {
  return languageString != null &&
      RtlLocalesRe.matcher(languageString).find();
}

See https://closure-templates.googlecode.com/svn-history/r21/trunk/java/src/com/google/template/soy/internal/i18n/BidiUtils.java