Extraction of language from MapsForge based file

MapDatabase.java

	/**
	 * Extracts substring of preferred language from multilingual string.<br/>
	 * Example multilingual string: "Base\ren\bEnglish\rjp\bJapan\rzh_py\bPin-yin".
	 * <p/>
	 * Use '\r' delimiter among names and '\b' delimiter between each language and name.
	 */
	private String extract(String s) {
		// check string
		if (s == null || s.trim().isEmpty()) {
			return null;
		}

		// prepare data
		String lang = mPreferredLanguage;
		String[] langNames = s.split("\r");

		// handle preferred language
		if (lang == null) {
			String[] langName = langNames[0].split("\b");
			if (langName.length == 1) {
				return langName[0];
			}

			// set english as default
			lang = "en";
		}

		// check possible languages
		String fallback = null;
		for (int i = 1; i < langNames.length; i++) {
			String[] langName = langNames[i].split("\b");
			if (langName.length != 2) {
				continue;
			}

			// Perfect match
			if (langName[0].equalsIgnoreCase(lang)) {
				return langName[1];
			}

			// Fall back to base, e.g. zh-min-lan -> zh
			if (fallback == null &&
					!langName[0].contains("-") &&
					(lang.contains("-") || lang.contains("_")) &&
					lang.toLowerCase(Locale.ENGLISH).startsWith(langName[0].toLowerCase(Locale.ENGLISH))) {
				fallback = langName[1];
			}
		}

		// return best default value
		if (fallback != null && fallback.length() > 0) {
			return fallback;
		}
		String[] langName = langNames[0].split("\b");
		if (langName.length == 2) {
			return langName[1];
		} else {
			return langNames[0];
		}
	}