阿拉伯数字转换为拼音读法

今天同学让看下这个题目，折腾了两个多小时，设计了个巨复杂的算法，漏洞百出。
回来的路上忽然想起来其实很简单啊，贴一下代码。
感叹一下，以后什么都要想好了再动手，那怕什么都不做，光思考了一大半时间，很多时候也比没想清楚急匆匆得开始干好得多。

import java.util.regex.Pattern;


public class num2pinyin {

    public static String numArray[] = {"Ling","Yi","Er","San","Si","Wu","Liu","Qi","Ba","Jiu"};
    //int范围到十亿就足够了
    public static String pinyinArray[] = {"","Shi","Bai","Qian","Wan","ShiWan","BaiWan","QianWan","Yii","ShiYii"};
    public static String Num2pinyin(int input)
    {
        StringBuilder sb = new StringBuilder();
        char[] nums = String.valueOf(input).toCharArray();
        for(int i=0;i<nums.length;i++)
        {
            int currentNum = nums[i] - '0';       
            sb.append(numArray[currentNum]);
            if(currentNum!=0)
                sb.append(pinyinArray[nums.length-1-i]);
        }
        String rst = sb.toString();
        //多个0替换成1个
        rst = rst.replaceAll("Ling(Ling)+", "Ling");
        //开头的“一十”换成“十”
        if(rst.startsWith("YiShi"))
            rst = rst.substring(2);
        
        //去掉末尾0
        if(rst.length()>4 && rst.endsWith("Ling"))
            rst = rst.substring(0, rst.length()-4);
        
        //出现多个亿的话只保留最后一个
        rst = remainLast(rst,"Yii");
        //亿后面再出现多个万的话只保留最后一个万
        rst = remainLast(rst,"Wan");        
        return rst;
    }
    //str 中删掉所有content，只保留最后一个
    public static String remainLast(String str,String content)
    {
        while(str.indexOf(content)!=str.lastIndexOf(content))
            str=str.replaceFirst(Pattern.quote(content), "");
        return str;
    }
    /**
     * @param args
     */
    public static void main(String[] args) {
        System.out.println(Num2pinyin(0));
        System.out.println(Num2pinyin(1));
        System.out.println(Num2pinyin(9));
        System.out.println(Num2pinyin(15));
        System.out.println(Num2pinyin(100));
        System.out.println(Num2pinyin(105));
        System.out.println(Num2pinyin(115));
        System.out.println(Num2pinyin(1001));
        System.out.println(Num2pinyin(2000));
        System.out.println(Num2pinyin(2100));
        System.out.println(Num2pinyin(2010));
        System.out.println(Num2pinyin(9999));
        System.out.println(Num2pinyin(10000));
        System.out.println(Num2pinyin(10001));
        System.out.println(Num2pinyin(10010));
        System.out.println(Num2pinyin(10100));
        System.out.println(Num2pinyin(21000));
        System.out.println(Num2pinyin(99999));
        System.out.println(Num2pinyin(100000));
        System.out.println(Num2pinyin(890909));
        System.out.println(Num2pinyin(2200000));
        System.out.println(Num2pinyin(2100000000));
    }

}