数字转换成英文

/**
 * Jessi初学英语，为了快速读出一串数字，编写程序将数字转换成英文： 如22：twenty two，123：one hundred and twenty
 * three。
 * 
 * 说明： 数字为正整数，长度不超过十位，不考虑小数，转化结果为英文小写； 非法数据请返回“error”；
 * 
 * 关键字：and，billion，million，thousand，hundred。

 */

package JavaExample2;

import java.util.Scanner;

public class Example6 {
	public static void main(String[] args) {
		Scanner scan = new Scanner(System.in);
		while (scan.hasNext()) {
			int number = scan.nextInt();
			String s = NumberToEnglishString(number);
			System.out.println(s);
		}
	}

	public static String NumberToEnglishString(int number) {
		String s = null;
		if (number < 0) {
			s = "error";
			return s;
		}
		if (number < 20) {
			switch (number) {
			case 0:
				s = "zero";
				return s;
			case 1:
				s = "one";
				return s;
			case 2:
				s = "two";
				return s;
			case 3:
				s = "three";
				return s;
			case 4:
				s = "four";
				return s;
			case 5:
				s = "five";
				return s;
			case 6:
				s = "six";
				return s;
			case 7:
				s = "seven";
				return s;
			case 8:
				s = "eight";
				return s;
			case 9:
				s = "nine";
				return s;
			case 10:
				s = "ten";
				return s;
			case 11:
				s = "eleven";
				return s;
			case 12:
				s = "twelve";
				return s;
			case 13:
				s = "thirteen";
				return s;
			case 14:
				s = "fourteen";
				return s;
			case 15:
				s = "fifteen";
				return s;
			case 16:
				s = "sixteen";
				return s;
			case 17:
				s = "seventeen";
				return s;
			case 18:
				s = "eighteen";
				return s;
			case 19:
				s = "nineteen";
				return s;
			default:
				s = "error";
				return s;
			}
		}

		if (number < 100) {
			if (number % 10 == 0) {
				switch (number) {
				case 20:
					s = "twenty";
					return s;
				case 30:
					s = "thirty";
					return s;
				case 40:
					s = "forty";
					return s;
				case 50:
					s = "fifty";
					return s;
				case 60:
					s = "sixty";
					return s;
				case 70:
					s = "seventy";
					return s;
				case 80:
					s = "eighty";
					return s;
				case 90:
					s = "ninety";
					return s;
				default:
					s = "error";
					return s;
				}
			} else {
				s = NumberToEnglishString(number / 10 * 10) + ' '
						+ NumberToEnglishString(number % 10);
				return s;
			}
		}

		if (number < 1000) {
			if (number % 100 == 0) {
				s = NumberToEnglishString(number / 100) + " hundred";
				return s;
			} else {
				s = NumberToEnglishString(number / 100) + " hundred and "
						+ NumberToEnglishString(number % 100);
				return s;
			}
		}

		if (number < 1000000) {
			if (number % 1000 == 0) {
				s = NumberToEnglishString(number / 1000) + " thousand";
				return s;
			} else {
				s = NumberToEnglishString(number / 1000) + " thousand "
						+ NumberToEnglishString(number % 1000);
				return s;
			}
		}

		if (number < 1000000000) {
			if (number % 1000000 == 0) {
				s = NumberToEnglishString(number / 1000000) + " million";
				return s;
			} else {
				s = NumberToEnglishString(number / 1000000) + " million "
						+ NumberToEnglishString(number % 1000000);
				return s;
			}
		}

		if (number < 999999999) {
			if (number % 1000000000 == 0) {
				s = NumberToEnglishString(number / 1000000000) + " billion";
				return s;
			} else {
				s = NumberToEnglishString(number / 1000000000) + " billion "
						+ NumberToEnglishString(number % 1000000000);
				return s;
			}
		}

		if (number > 999999999) {
			s = "error";
			return s;
		}
		return s;
	}
}