記得這是一道面試題，今天中午花時間寫了下，貼程式碼：

import java.util.Scanner;  

public class NumberToWord {  

   private static String input;

        private static Scanner sc;

        private static String[] num = {"零","一","二","三","四","五","六","七","八","九","十"};

        private static String[] unit = {"","十","百","千","萬"
 
,"十","百","千","億"};

        private static String[] result;

        private static void input() {
            System.out.println("請輸入一串數字最多9位");
            sc = new Scanner(System.in);
            input = sc.nextLine();
        }

        public static String transfer(String input) {
            String out
 
 = "";
            result = new String[input.length()];
            int length = result.length;
            for(int i = 0; i< length; i++) {
                result[i] = String.valueOf(input.charAt(i));
            }
            for(int i = 0; i< length; i++) {
                int back;
                if
 
(!result[i].equals("0")) {
                    back = length - i - 1;
                    out += num[Integer.parseInt(result[i])];
                    out += unit[back];
                } else {
                    //最後一位不考慮
                    if(i == (length - 1)) {
                        if(length > 4 && result[length - 1].equals("0") && result[length - 2].equals("0") && result[length - 3].equals("0") && result[length - 4].equals("0")){
                            out += unit[4];
                        }
                    } else {
                        //九位數，千萬，百萬，十萬，萬位都為0，則不加“萬”
                        if(length == 9 && result[1].equals("0") && result[2].equals("0") && result[3].equals("0") && result[4].equals("0")) {

                        } else {
                            //大於萬位，連著的兩個數不為0，萬位等於0則加上“萬”
                            if(length > 4 && !result[i+1].equals("0") && result[length -5].equals("0")){
                                out += unit[4];
                            }
                        }
                        //萬位之後的零顯示
                        if(i == length -4 && !result[i+1].equals("0")) {
                            out += num[0];
                        }
                    }
                }
            }
            return out;
        }
        public static void main(String[] args) {
            input();
            System.out.println(transfer(input));
        }

}

執行結果：

請輸入一串數字最多9位
10002345
一千萬二千三百四十五

請輸入一串數字最多9位
972364521
九億七千二百三十六萬四千五百二十一

請輸入一串數字最多9位
300000
三十萬