将中文数字转换成英文表示

public class NumberToWords {

private final String[] tensNames = {
"",
" ten",
" twenty",
" thirty",
" forty",
" fifty",
" sixty",
" seventy",
" eighty",
" ninety"
};

private final String[] numNames = {
"",
" one",
" two",
" three",
" four",
" five",
" six",
" seven",
" eight",
" nine",
" ten",
" eleven",
" twelve",
" thirteen",
" fourteen",
" fifteen",
" sixteen",
" seventeen",
" eighteen",
" nineteen"
};

private String convertLessThanOneThousand(int number) {
String soFar;

if (number % 100 < 20){
soFar = numNames[number % 100];
number /= 100;
}else {
soFar = numNames[number % 10];
number /= 10;

if(soFar.equals("")){
soFar = tensNames[number % 10] + soFar;
}else{
soFar = tensNames[number % 10] + " and " + soFar;
}
number /= 10;
}
if (number == 0){
return soFar;
}
return numNames[number] + " hundred" + soFar;
}

public String convert(long number) {
// 0 to 999 999 999 999
if (number == 0) { return "zero"; }

String snumber = Long.toString(number);

// pad with "0"
String mask = "000000000000";
DecimalFormat df = new DecimalFormat(mask);
snumber = df.format(number);

// XXXnnnnnnnnn
int billions = Integer.parseInt(snumber.substring(0,3));
// nnnXXXnnnnnn
int millions  = Integer.parseInt(snumber.substring(3,6));
// nnnnnnXXXnnn
int hundredThousands = Integer.parseInt(snumber.substring(6,9));
// nnnnnnnnnXXX
int thousands = Integer.parseInt(snumber.substring(9,12));

String tradBillions;
switch (billions) {
case 0:
tradBillions = "";
break;
case 1 :
tradBillions = convertLessThanOneThousand(billions)
+ " billion ";
break;
default :
tradBillions = convertLessThanOneThousand(billions)
+ " billion ";
}
String result =  tradBillions;

String tradMillions;
switch (millions) {
case 0:
tradMillions = "";
break;
case 1 :
tradMillions = convertLessThanOneThousand(millions)
+ " million ";
break;
default :
tradMillions = convertLessThanOneThousand(millions)
+ " million ";
}
result =  result + tradMillions;

String tradHundredThousands;
switch (hundredThousands) {
case 0:
tradHundredThousands = "";
break;
case 1 :
tradHundredThousands = "one thousand ";
break;
default :
tradHundredThousands = convertLessThanOneThousand(hundredThousands)
+ " thousand ";
}
result =  result + tradHundredThousands;

String tradThousand;
tradThousand = convertLessThanOneThousand(thousands);
result =  result + tradThousand;

// remove extra spaces!
return result.replaceAll("^\\s+", "").replaceAll("\\b\\s{2,}\\b", " ");
}

/**
* testing
* @param args
*/
public static void main(String[] args) {
NumberToWords nw = new NumberToWords();

System.out.println("*** " + nw.convert(1031));
System.out.println("*** " + nw.convert(1030));
System.out.println("*** " + nw.convert(0));
System.out.println("*** " + nw.convert(1));
System.out.println("*** " + nw.convert(36));
System.out.println("*** " + nw.convert(136));
System.out.println("*** " + nw.convert(1030));
System.out.println("*** " + nw.convert(1036));
System.out.println("*** " + nw.convert(1236));

System.out.println("*** " + nw.convert(3000000010L));

/*
*** zero
*** one
*** sixteen
*** one hundred
*** one hundred eighteen
*** two hundred
*** two hundred nineteen
*** eight hundred
*** eight hundred one
*** one thousand three hundred sixteen
*** one million
*** two millions
*** three millions two hundred
*** seven hundred thousand
*** nine millions
*** nine millions one thousand
*** one hundred twenty three millions four hundred
**      fifty six thousand seven hundred eighty nine
*** two billion one hundred forty seven millions
**      four hundred eighty three thousand six hundred forty seven
*** three billion ten
**/
}
}