Split camel case by using lookahead and lookbehind Zero-Length Assertions of regular expression

splitCamelCase

    /**
     * en: Split camel case by using lookahead and lookbehind Zero-Length Assertions of regular expression
     * ja:キャメルケースの分割。正規表現のゼロ幅先読みを使用
     *
     * @param hashTag
     * @return "camelCase" -> {"camel", "Case"}, "EMABiggestFans1D" -> {"EMA", "Biggest", "Fans", "1D"} , "MVDvsSSE" -> {"MVD", "SSE"}
     * @see <a href="http://msdn.microsoft.com/en-us/library/az24scfc(v=vs.110).aspx#grouping_constructs">Regular Expression Language - Quick Reference</a>
     * @see <a href="http://stackoverflow.com/questions/7593969/regex-to-split-camelcase-or-titlecase-advanced">java - RegEx to split camelCase or TitleCase (advanced) - Stack Overflow</a>
     */
    public static String[] splitCamelCase(String hashTag) {
        String[] tmp = hashTag.split("(?<=[A-Z0-9])vs?(?=[A-Z0-9])");
        if (tmp.length > 1) return tmp;

        return hashTag.split("(?<!(^|[A-Z0-9]))(?=[A-Z0-9])|(?<!^)(?=[A-Z][a-z])");
    }