30行，金额转人民币大写的代码

金额转人民币大写是一种常见的要求，但是这一看似简单的要求，实现起来却并不容易。

前不久，我被问到了这样一道题，当时写了个算法，昨天晚上又和BJDP的人们讨论了一下，觉得很有必要把这个算法写下来。

总共37行，去掉空行还不到30行，就不多啰嗦解释了。

public class ChineseCurrencyConverter {

    private static final String[] UNITS = {"亿","仟","佰","拾","万","仟","佰","拾","" };
    private static final String[] CHINESE_NUMBER = {"零","壹","贰","叁","肆","伍","陆","柒","捌","玖"};

    public static String convert(long yuan) {

        if (yuan >= 1e9 || yuan < 0) {
            return "这个数字超出解析范围了";
        }
        String amount = String.valueOf(yuan);
        int len = amount.length();
        int unitsLen = UNITS.length;

        String chineseCurrency = "";
        for (int i = len - 1; i >= 0; i--) {
            chineseCurrency = number(amount.charAt(i)) + unit(amount.charAt(i), unitsLen - len + i) +chineseCurrency;
        }

        chineseCurrency = chineseCurrency.replaceAll("零+","零");
        chineseCurrency =  chineseCurrency + "元整";
        chineseCurrency = chineseCurrency.replaceAll("零万","万");
        chineseCurrency = chineseCurrency.replaceAll("零元","元");
        return chineseCurrency;
    }

    private static String number(char number) {
        return CHINESE_NUMBER[Integer.parseInt(String.valueOf(number))];
    }

    private static String unit(char number, int pos) {
        if(number == '0' && pos != UNITS.length - 5) {
            return "";
        }
        return UNITS[pos];
    }
}

下面是一些用来测试的代码：

public class TestConverter  {

    public static void main(String[] args) {
        System.out.println(ChineseCurrencyConverter.convert(100));
        System.out.println(ChineseCurrencyConverter.convert(130));
        System.out.println(ChineseCurrencyConverter.convert(102));
        System.out.println(ChineseCurrencyConverter.convert(124));
        System.out.println(ChineseCurrencyConverter.convert(1000));
        System.out.println(ChineseCurrencyConverter.convert(10000));
        System.out.println(ChineseCurrencyConverter.convert(100000));
        System.out.println(ChineseCurrencyConverter.convert(1000000));
        System.out.println(ChineseCurrencyConverter.convert(10000000));
        System.out.println(ChineseCurrencyConverter.convert(10000000));
        System.out.println(ChineseCurrencyConverter.convert(100000000));
        System.out.println(ChineseCurrencyConverter.convert(1000000000));
        System.out.println(ChineseCurrencyConverter.convert(1002));
        System.out.println(ChineseCurrencyConverter.convert(1020));
        System.out.println(ChineseCurrencyConverter.convert(1200));
        System.out.println(ChineseCurrencyConverter.convert(10003));
        System.out.println(ChineseCurrencyConverter.convert(10030));
        System.out.println(ChineseCurrencyConverter.convert(10033));
        System.out.println(ChineseCurrencyConverter.convert(10330));
        System.out.println(ChineseCurrencyConverter.convert(13030));
        System.out.println(ChineseCurrencyConverter.convert(100030));
        System.out.println(ChineseCurrencyConverter.convert(100003));
        System.out.println(ChineseCurrencyConverter.convert(100300));
        System.out.println(ChineseCurrencyConverter.convert(103000));
        System.out.println(ChineseCurrencyConverter.convert(100303));
        System.out.println(ChineseCurrencyConverter.convert(1000004));
        System.out.println(ChineseCurrencyConverter.convert(10000005));
        System.out.println(ChineseCurrencyConverter.convert(10000006));
        System.out.println(ChineseCurrencyConverter.convert(12000006));
        System.out.println(ChineseCurrencyConverter.convert(10030006));
        System.out.println(ChineseCurrencyConverter.convert(10200006));
        System.out.println(ChineseCurrencyConverter.convert(100000007));
        System.out.println(ChineseCurrencyConverter.convert(1000000008));

    }
}

这些数字测试的结果还都正确。

这里没有处理角和分，留给有想法的同学去尝试一下吧。