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;
}
}