金额大写转换

import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class TestAA {
    private static final Pattern AMOUNT_PATTERN = Pattern.compile("^(0|[1-9]\\d{0,11})\\.(\\d\\d)$");
    private static final char[] RMB_NUMS = {'零','壹','贰','叁','肆','伍','陆','柒','捌','玖'};
    private static final String[] UNITS = {"元","角","分","整"};
    private static final String[] U1 = {"","拾","佰","仟"};
    private static final String[] U2 = {"","万","亿"};
    public static void main(String[] args) {
        String convert = convert(String.valueOf(10.23));
        System.out.println(convert);
    }

    public static String convert(String amount) throws IllegalArgumentException {
        Matcher matcher = AMOUNT_PATTERN.matcher(amount);
        if (! matcher.find()) {
            throw new IllegalArgumentException("金额格式不正确");
        }
        String integer  = matcher.group(1);
        String fraction = matcher.group(2);

        String result = "";
        if (! integer.equals("0")) {
            result += integer2rmb(integer) + UNITS[0];
        }
        if (fraction.equals("00")) {
            result += UNITS[3];
        } else if (fraction.startsWith("0") && integer.equals("0")) {
            result += fraction2rmb(fraction).substring(1);
        } else {
            result += fraction2rmb(fraction);
        }
        return result;
    }
    private static String fraction2rmb(String fraction) {
        char jiao = fraction.charAt(0);
        char fen  = fraction.charAt(1);
        return (RMB_NUMS[jiao - '0'] + (jiao > '0' ? UNITS[1] : ""))
                + (fen > '0' ? RMB_NUMS[fen - '0'] + UNITS[2] : "");
    }
    private static String integer2rmb(String integer) {
        StringBuilder buffer = new StringBuilder();
        int i, j;
        for (i = integer.length() - 1, j = 0; i >= 0; i--, j++) {
            char n = integer.charAt(i);
            if (n == '0') {
                if (i < integer.length() - 1 && integer.charAt(i + 1) != '0') {
                    buffer.append(RMB_NUMS[0]);
                }
                if (j % 4 == 0) {
                    if (i > 0 && integer.charAt(i - 1) != '0'
                            || i > 1 && integer.charAt(i - 2) != '0'
                            || i > 2 && integer.charAt(i - 3) != '0') {
                        buffer.append(U2[j / 4]);
                    }
                }
            } else {
                if (j % 4 == 0) {
                    buffer.append(U2[j / 4]);
                }
                buffer.append(U1[j % 4]);
                buffer.append(RMB_NUMS[n - '0']);
            }
        }
        return buffer.reverse().toString();
    }
}