Hundred: 100
Thousand:1,000
Million: 1,000,000
Billion: 1,000,000,000
Trillion: 1,000,000,000,000
Quintillion: 1,000,000,000,000,000,000
Sextillion: 1,000,000,000,000,000,000,000
Nonillion: 1,000,000,000,000,000,000,000,000,000,000
Centillion: 1 followed by 303 zeros

public class NumUtil {
 public static final String[] enNum = { // 基本數(shù)詞表
 "zero", "one", "tow", "three", "four", "five", "six", "seven", "eight",
  "nine", "ten", "eleven", "twelve", "thirteen", "fourteen",
  "fifteen", "sixteen", "seventeen", "eighteen", "nineteen",
  "twenty", "", "", "", "", "", "", "", "", "", "thirty", "", "", "",
  "", "", "", "", "", "", "fourty", "", "", "", "", "", "", "", "",
  "", "fifty", "", "", "", "", "", "", "", "", "", "sixty", "", "",
  "", "", "", "", "", "", "", "seventy", "", "", "", "", "", "", "",
  "", "", "eighty", "", "", "", "", "", "", "", "", "", "ninety" };
 public static final String[] enUnit = { "hundred", "thousand", "million",
  "billion", "trillion", "quintillion" }; // 單位表
 public static void main(String[] args) {
 System.out.println(analyze(1)); // 測試數(shù)據(jù)
 System.out.println(analyze(21));
 System.out.println(analyze(105));
 System.out.println(analyze(3250));
 System.out.println(analyze(47826));
 System.out.println(analyze(56945781));
 }
 public static String analyze(long num) {
 // long型參數(shù)，
 return analyze(String.valueOf(num));
 // 因為long型有極限，所以以字符串參數(shù)方法為主
 }
 public static String analyze(String num) {
 // 數(shù)字字符串參數(shù)
 // 判斷字符串是否為數(shù)字
 if (!num.matches("\\d+")) {
  return String.format("%s is not number", num);
 }
 num = num.replaceAll("^[0]*([1-9]*)", "$1");
 // 把字符串前面的0去掉
 if (num.length() == 0) {
 // 如果長度為0，則原串都是0
  return enNum[0];
 } else if (num.length() > 9) {
 // 如果大于9，即大于999999999，題目限制條件
  return "too big";
 }
 // 按3位分割分組
 int count = (num.length() % 3 == 0) ? num.length() / 3
  : num.length() / 3 + 1;
 if (count > enUnit.length) {
  return "too big";
 } // 判斷組單位是否超過，
 // 可以根據(jù)需求適當(dāng)追加enUnit
 String[] group = new String[count];
 for (int i = num.length(), j = group.length - 1; i > 0; i -= 3) {
  group[j--] = num.substring(Math.max(i - 3, 0), i);
 }
 StringBuilder buf = new StringBuilder(); // 結(jié)果保存
 for (int i = 0; i < count; i++) { // 遍歷分割的組
  int v = Integer.valueOf(group[i]);
  if (v >= 100) { // 因為按3位分割，所以這里不會有超過999的數(shù)
  buf.append(enNum[v / 100]).append(" ").append(enUnit[0])
   .append(" ");
  v = v % 100; // 獲取百位，并得到百位以后的數(shù)
  if (v != 0) {
   buf.append("and ");
  } // 如果百位后的數(shù)不為0，則追加and
  }
  if (v != 0) { // 前提是v不為0才作解析
  if (v < 20 || v % 10 == 0) {
  // 如果小于20或10的整數(shù)倍，直接取基本數(shù)詞表的單詞
   buf.append(enNum[v]).append(" ");
  } else { // 否則取10位數(shù)詞，再取個位數(shù)詞
   buf.append(enNum[v - v % 10]).append(" ");
   buf.append(enNum[v % 10]).append(" ");
  }
  if (i != count - 1) { // 百位以上的組追加相應(yīng)的單位
   buf.append(enUnit[count - 1 - i]).append(" ");
  }
  }
 }
 return buf.toString().trim(); // 返回值
 }
}