You will produce a short, elegant, recursive algorithm that spells out any numbe

Question

You will produce a short, elegant, recursive algorithm that spells out any number between 1 and 2.1 billion. Allow the user to input a number in the range from 1 to 2.1 billion (a positive 32-bit int), then spell out the number (e.g. 123456 would output "one hundred twenty three thousand four hundred fifty six"). Chap12 updated2say has a simple flow diagram that could represent the logic you use for this. Use a recursive method "say(n)" where n) returns the string corresponding to the input integer n. The beauty of recursion is that this can be done with just a few if statements and switch case values (about 30 or so tot thanks to the way we read numbers (the number 123, 123, 123 is spoken the same as a single 123. but with a few "place" words million, thousand, etc.). Deliverable: Saymynumber.java

Explanation / Answer

import java.text.DecimalFormat;

public class Saymynumber {

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

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

private Saymynumber() {}

private static String convertLessThanOneThousand(int number) {
String soFar;

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

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

public static 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) {
System.out.println("*** " + Saymynumber.convert(0));
System.out.println("*** " + Saymynumber.convert(1));
System.out.println("*** " + Saymynumber.convert(16));
System.out.println("*** " + Saymynumber.convert(100));
System.out.println("*** " + Saymynumber.convert(118));
System.out.println("*** " + Saymynumber.convert(200));
System.out.println("*** " + Saymynumber.convert(219));
System.out.println("*** " + Saymynumber.convert(800));
System.out.println("*** " + Saymynumber.convert(801));
System.out.println("*** " + Saymynumber.convert(1316));
System.out.println("*** " + Saymynumber.convert(1000000));
System.out.println("*** " + Saymynumber.convert(2000000));
System.out.println("*** " + Saymynumber.convert(3000200));
System.out.println("*** " + Saymynumber.convert(700000));
System.out.println("*** " + Saymynumber.convert(9000000));
System.out.println("*** " + Saymynumber.convert(9001000));
System.out.println("*** " + Saymynumber.convert(123456789));
System.out.println("*** " + Saymynumber.convert(2147483647));
System.out.println("*** " + Saymynumber.convert(3000000010L));
}
}

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