Emoji expression conversion tool

import java.io.UnsupportedEncodingException;
import java.net.URLDecoder;
import java.net.URLEncoder;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * Emoji conversion tools
 *
 * @version $ID$
 * @since 2018/11/12 13:44
 */
public class EmojiUtil {
    static final Logger LOGGER = LoggerFactory.getLogger(EmojiUtil.class);

    /**
     * Convert emoji expressions into strings
     *
     * @param str
     *
     * @return
     *
     * @throws UnsupportedEncodingException
     */
    public static String emojiEncode(String str) throws UnsupportedEncodingException {
        String patternString = "([\\x{10000}-\\x{10ffff}\ud800-\udfff])";
        Pattern pattern = Pattern.compile(patternString);
        Matches matches = pattern.matcher (str);
        StringBuffer sb = new StringBuffer();
        while (matcher.find()) {
            try {
                matcher.appendReplacement(sb, "[[" + URLEncoder.encode(matcher.group(1), "UTF-8") + "]]");
            } catch (UnsupportedEncodingException e) {
                LOGGER.error("emojiEncode error", e);
                throw e;
            }
        }
        matcher.appendTail(sb);
        LOGGER.debug("emojiEncode " + str + " to " + sb.toString() + ", len：" + sb.length());
        return sb.toString();
    }

    /**
     * Convert the containing string into emoji expressions
     * @param str
     *
     * @return
     *
     * @throws UnsupportedEncodingException
     *         exception
     */
    public static String emojiDecode(String str) throws UnsupportedEncodingException {
        String patternString = "\\[\\[(.*?)\\]\\]";

        Pattern pattern = Pattern.compile(patternString);
        Matches matches = pattern.matcher (str);

        StringBuffer sb = new StringBuffer();
        while (matcher.find()) {
            try {
                matcher.appendReplacement(sb, URLDecoder.decode(matcher.group(1), "UTF-8"));
            } catch (UnsupportedEncodingException e) {
                LOGGER.error("emojiDecode error", e);
                throw e;
            }
        }
        matcher.appendTail(sb);
        LOGGER.debug("emojiDecode " + str + " to " + sb.toString());
        return sb.toString();
    }
}