How to convert number to words in java

Question

We currently have a crude mechanism to convert numbers to words (e.g. using a few static arrays) and based on the size of the number translating that into an english text. B

Answer 1

I think that this solution is not the best, since it works only for int, but i think it's great for a beginner.

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

    public static final String[] tens = {
            "",        // 0
            "",        // 1
            "twenty",  // 2
            "thirty",  // 3
            "forty",   // 4
            "fifty",   // 5
            "sixty",   // 6
            "seventy", // 7
            "eighty",  // 8
            "ninety"   // 9
    };

    public static String convert(final int n) {
        if (n < 0) {
            return "minus " + convert(-n);
        }

        if (n < 20) {
            return units[n];
        }

        if (n < 100) {
            return tens[n / 10] + ((n % 10 != 0) ? " " : "") + units[n % 10];
        }

        if (n < 1000) {
            return units[n / 100] + " hundred" + ((n % 100 != 0) ? " " : "") + convert(n % 100);
        }

        if (n < 1000000) {
            return convert(n / 1000) + " thousand" + ((n % 1000 != 0) ? " " : "") + convert(n % 1000);
        }

        if (n < 1000000000) {
            return convert(n / 1000000) + " million" + ((n % 1000000 != 0) ? " " : "") + convert(n % 1000000);
        }

        return convert(n / 1000000000) + " billion"  + ((n % 1000000000 != 0) ? " " : "") + convert(n % 1000000000);
    }

    public static void main(final String[] args) {
        final Random generator = new Random();

        int n;
        for (int i = 0; i < 20; i++) {
            n = generator.nextInt(Integer.MAX_VALUE);

            System.out.printf("%10d = '%s'%n", n, convert(n));
        }

        n = 1000;
        System.out.printf("%10d = '%s'%n", n, convert(n));

        n = 2000;
        System.out.printf("%10d = '%s'%n", n, convert(n));

        n = 10000;
        System.out.printf("%10d = '%s'%n", n, convert(n));

        n = 11000;
        System.out.printf("%10d = '%s'%n", n, convert(n));

        n = 999999999;
        System.out.printf("%10d = '%s'%n", n, convert(n));

        n = Integer.MAX_VALUE;
        System.out.printf("%10d = '%s'%n", n, convert(n));
    }
}

The test creates 20 random numbers up to Integer.MAX_VALUE and than some that know to be problematic, because of 0, 10, etc.. Output:

   5599908 = 'five million five hundred ninety nine thousand nine hundred eight'
 192603486 = 'one hundred ninety two million six hundred three thousand four hundred eighty six'
1392431868 = 'one billion three hundred ninety two million four hundred thirty one thousand eight hundred sixty eight'
1023787010 = 'one billion twenty three million seven hundred eighty seven thousand ten'
1364396236 = 'one billion three hundred sixty four million three hundred ninety six thousand two hundred thirty six'
1511255671 = 'one billion five hundred eleven million two hundred fifty five thousand six hundred seventy one'
 225955221 = 'two hundred twenty five million nine hundred fifty five thousand two hundred twenty one'
1890141052 = 'one billion eight hundred ninety million one hundred forty one thousand fifty two'
 261839422 = 'two hundred sixty one million eight hundred thirty nine thousand four hundred twenty two'
 728428650 = 'seven hundred twenty eight million four hundred twenty eight thousand six hundred fifty'
 860607319 = 'eight hundred sixty million six hundred seven thousand three hundred nineteen'
 719753587 = 'seven hundred nineteen million seven hundred fifty three thousand five hundred eighty seven'
2063829124 = 'two billion sixty three million eight hundred twenty nine thousand one hundred twenty four'
1081010996 = 'one billion eighty one million ten thousand nine hundred ninety six'
 999215799 = 'nine hundred ninety nine million two hundred fifteen thousand seven hundred ninety nine'
2105226236 = 'two billion one hundred five million two hundred twenty six thousand two hundred thirty six'
1431882940 = 'one billion four hundred thirty one million eight hundred eighty two thousand nine hundred forty'
1991707241 = 'one billion nine hundred ninety one million seven hundred seven thousand two hundred forty one'
1088301563 = 'one billion eighty eight million three hundred one thousand five hundred sixty three'
 964601609 = 'nine hundred sixty four million six hundred one thousand six hundred nine'
      1000 = 'one thousand'
      2000 = 'two thousand'
     10000 = 'ten thousand'
     11000 = 'eleven thousand'
 999999999 = 'nine hundred ninety nine million nine hundred ninety nine thousand nine hundred ninety nine'
2147483647 = 'two billion one hundred forty seven million four hundred eighty three thousand six hundred forty seven'

Hope it helps :)