见微知著： StringUtils.split

 public static void main(String[] args) {
        String input = "this is a demo, this \"，\"is a \"demo";
        String[] split = StringUtils.split(input,"\"，\"");
        for(String str: split){
            System.out.println(str);
        }
    }

this is a demo, this 
is a 
demo

 /**
     * <p>Splits the provided text into an array, separators specified.
     * This is an alternative to using StringTokenizer.</p>
     *
     * <p>The separator is not included in the returned String array.
     * Adjacent separators are treated as one separator.
     * For more control over the split use the StrTokenizer class.</p>
     *
     * <p>A {@code null} input String returns {@code null}.
     * A {@code null} separatorChars splits on whitespace.</p>
     *
     * <pre>
     * StringUtils.split(null, *)         = null
     * StringUtils.split("", *)           = []
     * StringUtils.split("abc def", null) = ["abc", "def"]
     * StringUtils.split("abc def", " ")  = ["abc", "def"]
     * StringUtils.split("abc  def", " ") = ["abc", "def"]
     * StringUtils.split("ab:cd:ef", ":") = ["ab", "cd", "ef"]
     * </pre>
     *
     * @param str  the String to parse, may be null
     * @param separatorChars  the characters used as the delimiters,
     *  {@code null} splits on whitespace
     * @return an array of parsed Strings, {@code null} if null String input
     */
    public static String[] split(final String str, final String separatorChars) {
        return splitWorker(str, separatorChars, -1, false);
    }

 /**
     * Performs the logic for the {@code split} and
     * {@code splitPreserveAllTokens} methods that return a maximum array
     * length.
     *
     * @param str  the String to parse, may be {@code null}
     * @param separatorChars the separate character
     * @param max  the maximum number of elements to include in the
     *  array. A zero or negative value implies no limit.
     * @param preserveAllTokens if {@code true}, adjacent separators are
     * treated as empty token separators; if {@code false}, adjacent
     * separators are treated as one separator.
     * @return an array of parsed Strings, {@code null} if null String input
     */
    private static String[] splitWorker(final String str, final String separatorChars, final int max, final boolean preserveAllTokens) {
        // Performance tuned for 2.0 (JDK1.4)
        // Direct code is quicker than StringTokenizer.
        // Also, StringTokenizer uses isSpace() not isWhitespace()

        if (str == null) {
            return null;
        }
        final int len = str.length();
        if (len == 0) {
            return ArrayUtils.EMPTY_STRING_ARRAY;
        }
        final List<String> list = new ArrayList<>();
        int sizePlus1 = 1;
        int i = 0;
        int start = 0;
        boolean match = false;
        boolean lastMatch = false;
        if (separatorChars == null) {
            // 省略
        } else if (separatorChars.length() == 1) {
            // 省略
        } else {
            // standard case
            while (i < len) {
                if (separatorChars.indexOf(str.charAt(i)) >= 0) {
                    if (match || preserveAllTokens) {
                        lastMatch = true;
                        if (sizePlus1++ == max) {
                            i = len;
                            lastMatch = false;
                        }
                        list.add(str.substring(start, i));
                        match = false;
                    }
                    start = ++i;
                    continue;
                }
                lastMatch = false;
                match = true;
                i++;
            }
        }
        if (match || preserveAllTokens && lastMatch) {
            list.add(str.substring(start, i));
        }
        return list.toArray(ArrayUtils.EMPTY_STRING_ARRAY);
    }

   public static void main(String[] args) {
        String input = "this is a demo, this \"，\"is a \"demo";
        String[] split = input.split("\"，\"");
        for(String str: split){
            System.out.println(str);
        }
    }

    /**
     * Splits this string around matches of the given <a
     * href="../util/regex/Pattern.html#sum">regular expression</a>.
     *
     * <p> This method works as if by invoking the two-argument {@link
     * #split(String, int) split} method with the given expression and a limit
     * argument of zero.  Trailing empty strings are therefore not included in
     * the resulting array.
     *
     * <p> The string {@code "boo:and:foo"}, for example, yields the following
     * results with these expressions:
     *
     * <blockquote><table cellpadding=1 cellspacing=0 summary="Split examples showing regex and result">
     * <tr>
     *  <th>Regex</th>
     *  <th>Result</th>
     * </tr>
     * <tr><td align=center>:</td>
     *     <td>{@code { "boo", "and", "foo" }}</td></tr>
     * <tr><td align=center>o</td>
     *     <td>{@code { "b", "", ":and:f" }}</td></tr>
     * </table></blockquote>
     *
     *
     * @param  regex
     *         the delimiting regular expression
     *
     * @return  the array of strings computed by splitting this string
     *          around matches of the given regular expression
     *
     * @throws  PatternSyntaxException
     *          if the regular expression's syntax is invalid
     *
     * @see java.util.regex.Pattern
     *
     * @since 1.4
     * @spec JSR-51
     */
    public String[] split(String regex) {
        return split(regex, 0);
    }