NumberToWords.java

package javacodes;

/*Given a number, you have to write it in words*/
import java.io.*;
import java.util.*;
//number to word
class NumberToWords {

    public static void main(String[] args) throws IOException {
        DataInputStream in = new DataInputStream(System.in);
        int t, l, x, y;
        String s, ans;
        // initializing the strings to store the words for each number
        String l19[] = {"", "One ", "Two ", "Three ", "Four ", "Five ", "Six ", "Seven ", "Eight ", "Nine ", "Ten ", "Eleven ", "Twelve ", "Thirteen ", "Fourteen ", "Fifteen ", "Sixteen ", "Seventeen ", "Eighteen ", "Nineteen "};
        String l90[] = {"", "", "Twenty ", "Thirty ", "Forty ", "Fifty ", "Sixty ", "Seventy ", "Eighty ", "Ninety "};
        //System.out.println("Enter input:");
        t = Integer.parseInt(in.readLine());    //taking number as input
        while (t > 0) {
            ans = "";
            int c = 12;
            s = in.readLine();
            l = s.length();
            int n[] = new int[13];
            for (int i = l - 1; i >= 0; i--, c--) {
                n[c] = s.charAt(i) - 48;    //extracting character and converting character to integer
            }
            y = 0;
            for (int i = ++c; i < 13; i++) {
                switch (i) {    //switch case
                    case 0:
                        if (n[i] == 0) {
                            break;
                        }
                        ans = ans + l19[n[i]] + "Trillion ";
                        break;
                    case 1:
                    case 7:
                    case 4:
                    case 10:
                        if (n[i] == 0) {
                            break;
                        }
                        ans = ans + l19[n[i]] + "Hundred ";
                        y = n[i];
                        break;
                    case 2:
                    case 5:
                    case 8:
                    case 11:
                        x = n[i] * 10 + n[i + 1];
                        y = y * 100 + x;
                        if (y == 0) {
                            break;
                        }
                        if (x < 20) {
                            ans = ans + l19[x];
                        } else {
                            ans = ans + l90[n[i]] + l19[n[i + 1]];
                        }
                        i++;
                        break;
                    case 3:
                    case 6:
                    case 9:
                    case 12:
                        y = n[i];
                        if (y == 0) {
                            break;
                        }
                        ans = ans + l19[y];
                        break;
                }
                if (i - 1 == 2 && y != 0) {
                    ans = ans + "Billion ";
                    y = 0;
                }
                if (i - 1 == 5 && y != 0) {
                    ans = ans + "Million ";
                    y = 0;
                }
                if (i - 1 == 8 && y != 0) {
                    ans = ans + "Thousand ";
                    y = 0;
                }
            }
            System.out.println(ans.trim());
            t--;
        }
    }
}