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。

 1 public class ChineseCurrencyConverter {
 2 
 3     private static final String[] UNITS = {"亿","仟","佰","拾","万","仟","佰","拾","" };
 4     private static final String[] CHINESE_NUMBER = {"零","壹","贰","叁","肆","伍","陆","柒","捌","玖"};
 5 
 6     public static String convert(long yuan) {
 7 
 8         if (yuan >= 1e9 || yuan < 0) {
 9             return "这个数字超出解析范围了";
10         }
11         String amount = String.valueOf(yuan);
12         int len = amount.length();
13         int unitsLen = UNITS.length;
14 
15         String chineseCurrency = "";
16         for (int i = len - 1; i >= 0; i--) {
17             chineseCurrency = number(amount.charAt(i)) + unit(amount.charAt(i), unitsLen - len + i) +chineseCurrency;
18         }
19 
20         chineseCurrency = chineseCurrency.replaceAll("零+","零");
21         chineseCurrency =  chineseCurrency + "元整";
22         chineseCurrency = chineseCurrency.replaceAll("零万","万");
23         chineseCurrency = chineseCurrency.replaceAll("零元","元");
24         return chineseCurrency;
25     }
26 
27     private static String number(char number) {
28         return CHINESE_NUMBER[Integer.parseInt(String.valueOf(number))];
29     }
30 
31     private static String unit(char number, int pos) {
32         if(number == '0' && pos != UNITS.length - 5) {
33             return "";
34         }
35         return UNITS[pos];
36     }
37 }

下面是一些用来测试的代码：

 1 public class TestConverter  {
 2 
 3     public static void main(String[] args) {
 4         System.out.println(ChineseCurrencyConverter.convert(100));
 5         System.out.println(ChineseCurrencyConverter.convert(130));
 6         System.out.println(ChineseCurrencyConverter.convert(102));
 7         System.out.println(ChineseCurrencyConverter.convert(124));
 8         System.out.println(ChineseCurrencyConverter.convert(1000));
 9         System.out.println(ChineseCurrencyConverter.convert(10000));
10         System.out.println(ChineseCurrencyConverter.convert(100000));
11         System.out.println(ChineseCurrencyConverter.convert(1000000));
12         System.out.println(ChineseCurrencyConverter.convert(10000000));
13         System.out.println(ChineseCurrencyConverter.convert(10000000));
14         System.out.println(ChineseCurrencyConverter.convert(100000000));
15         System.out.println(ChineseCurrencyConverter.convert(1000000000));
16         System.out.println(ChineseCurrencyConverter.convert(1002));
17         System.out.println(ChineseCurrencyConverter.convert(1020));
18         System.out.println(ChineseCurrencyConverter.convert(1200));
19         System.out.println(ChineseCurrencyConverter.convert(10003));
20         System.out.println(ChineseCurrencyConverter.convert(10030));
21         System.out.println(ChineseCurrencyConverter.convert(10033));
22         System.out.println(ChineseCurrencyConverter.convert(10330));
23         System.out.println(ChineseCurrencyConverter.convert(13030));
24         System.out.println(ChineseCurrencyConverter.convert(100030));
25         System.out.println(ChineseCurrencyConverter.convert(100003));
26         System.out.println(ChineseCurrencyConverter.convert(100300));
27         System.out.println(ChineseCurrencyConverter.convert(103000));
28         System.out.println(ChineseCurrencyConverter.convert(100303));
29         System.out.println(ChineseCurrencyConverter.convert(1000004));
30         System.out.println(ChineseCurrencyConverter.convert(10000005));
31         System.out.println(ChineseCurrencyConverter.convert(10000006));
32         System.out.println(ChineseCurrencyConverter.convert(12000006));
33         System.out.println(ChineseCurrencyConverter.convert(10030006));
34         System.out.println(ChineseCurrencyConverter.convert(10200006));
35         System.out.println(ChineseCurrencyConverter.convert(100000007));
36         System.out.println(ChineseCurrencyConverter.convert(1000000008));
37 
38     }
39 }