BSD number.c in Java

NumberConverter.java

/*
 * Copyright (c) 1988, 1993, 1994
 *	The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

package org.tinnedfruit.number;

import java.math.BigDecimal;
import java.math.BigInteger;
import java.math.RoundingMode;

/**
 * This class is a Java port of the number.c program from the BSD Games package.
 * The original C code was converted to Java by Gemini for use as a Java library.
 * The purpose of this class is to convert numeric values into their textual
 * representations.
 * <p>
 * Only this paragraph, the copyright header, and the package name has been written
 * by a human. The rest of the output is entirely from Gemini 2.0 Flash.
 * The prompt was a paste of 
 * <a href="https://raw.githubusercontent.com/vattam/BSDGames/04f8d1635706cc7f67fd8c75bccdafe70ee8b084/number/number.c">number.c</a>
 * with a request to port the code to Java for use as a library.
 */
public class NumberConverter {

    private static final String[] name1 = {
            "", "one", "two", "three",
            "four", "five", "six", "seven",
            "eight", "nine", "ten", "eleven",
            "twelve", "thirteen", "fourteen", "fifteen",
            "sixteen", "seventeen", "eighteen", "nineteen",
    };

    private static final String[] name2 = {
            "", "ten", "twenty", "thirty",
            "forty", "fifty", "sixty", "seventy",
            "eighty", "ninety",
    };

    private static final String[] name3 = {
            "hundred", "thousand", "million", "billion",
            "trillion", "quadrillion", "quintillion", "sextillion",
            "septillion", "octillion", "nonillion", "decillion",
            "undecillion", "duodecillion", "tredecillion", "quattuordecillion",
            "quindecillion", "sexdecillion",
            "septendecillion", "octodecillion",
            "novemdecillion", "vigintillion",
    };

    private boolean lflag; // Instance variable, can be set per instance
    private static final int MAXNUM = 65;

    // Constructor to set lflag (for future customization)
    public NumberConverter(boolean lflag) {
        this.lflag = lflag;
    }

    // Default constructor
    public NumberConverter() {
        this(false); // Default lflag to false
    }

    public String convert(int number) {
        return convert(String.valueOf(number));
    }

    public String convert(long number) {
        return convert(String.valueOf(number));
    }

    public String convert(float number) {
        return convert(String.valueOf(number)); // Convert to string to handle decimal part
    }

    public String convert(double number) {
        return convert(String.valueOf(number)); // Convert to string to handle decimal part
    }

    public String convert(BigDecimal number) {
        return convert(number.toString());
    }


    public String convert(String line) {
        StringBuilder result = new StringBuilder();
        String fraction = null;
        int flen = 0;
        String mainNumber = line.trim();

        if (mainNumber.isEmpty()) {
            return "zero" + (lflag ? "" : ".");
        }

        if (mainNumber.contains(".")) {
            int dotIndex = mainNumber.indexOf(".");
            fraction = mainNumber.substring(dotIndex + 1);
            mainNumber = mainNumber.substring(0, dotIndex);
        }

        if (mainNumber.startsWith("-")) {
            result.append("minus").append(lflag ? " " : "\n");
            mainNumber = mainNumber.substring(1);
        }

        if (!mainNumber.matches("-?\\d*") || (fraction != null && !fraction.matches("\\d*"))) {
            throw new IllegalArgumentException("illegal number: " + line);
        }

        int len = mainNumber.length();
        if (fraction != null) {
            flen = fraction.length();
        }

        if (len > MAXNUM || flen > MAXNUM) {
            throw new IllegalArgumentException("number too large, max " + MAXNUM + " digits.");
        }

        int[] singular = new int[1];
        boolean rval = len > 0 ? unit(len, mainNumber, singular, result) : false;

        if (fraction != null && flen > 0) {
            boolean fractionNonZero = false;
            for (int i = 0; i < flen; i++) {
                if (fraction.charAt(i) != '0') {
                    fractionNonZero = true;
                    break;
                }
            }

            if (fractionNonZero) {
                if (rval) {
                    result.append((lflag ? " " : "and")).append(lflag ? " " : "\n");
                }
                if (unit(flen, fraction, singular, result)) {
                    if (lflag) {
                        result.append(" ");
                    }
                    pfract(flen, singular[0], result);
                    rval = true;
                }
            }
        }

        if (!rval) {
            result.append("zero").append(lflag ? "" : ".");
            if (!lflag) result.append("\n");
        }
        return result.toString();
    }

    private boolean unit(int len, String p, int[] singular, StringBuilder result) {
        boolean rval = false;
        if (len > 3) {
            if (len % 3 != 0) {
                int off = len % 3;
                len -= off;
                if (number(p.substring(0, off), off, singular, result)) {
                    rval = true;
                    result.append(" ").append(name3[len / 3]).append(lflag ? " " : ".\n");
                }
                p = p.substring(off);
            }
            while (len > 3) {
                len -= 3;
                if (number(p.substring(0, 3), 3, singular, result)) {
                    rval = true;
                    result.append(" ").append(name3[len / 3]).append(lflag ? " " : ".\n");
                }
                p = p.substring(3);
            }
        }
        if (number(p, len, singular, result)) {
            if (rval)
                singular[0] = 0;
            if (!lflag)
                result.append(".\n");
            rval = true;
        }
        return rval;
    }

    private boolean number(String p, int len, int[] singular, StringBuilder result) {
        int val;
        boolean rval = false;

        singular[0] = 1;
        switch (len) {
            case 3:
                if (p.charAt(0) != '0') {
                    rval = true;
                    singular[0] = 0;
                    result.append(name1[p.charAt(0) - '0']).append(" hundred");
                }
                p = p.substring(1);
            case 2:
                val = (p.charAt(1) - '0') + (p.charAt(0) - '0') * 10;
                if (val != 0) {
                    if (rval)
                        result.append(" ");
                    if (val < 20)
                        result.append(name1[val]);
                    else {
                        result.append(name2[val / 10]);
                        if (val % 10 != 0)
                            result.append("-").append(name1[val % 10]);
                    }
                    rval = true;
                }
                if (val != 1)
                    singular[0] = 0;
                break;
            case 1:
                if (p.charAt(0) != '0') {
                    rval = true;
                    result.append(name1[p.charAt(0) - '0']);
                }
                if (p.charAt(0) != '1')
                    singular[0] = 0;
                break;
        }
        return rval;
    }

    private void pfract(int len, int singular, StringBuilder result) {
        String[] pref = {"", "ten-", "hundred-"};

        switch (len) {
            case 1:
                result.append("tenth");
                break;
            case 2:
                result.append("hundredth");
                break;
            default:
                result.append(pref[len % 3]).append(name3[len / 3]).append("th");
                break;
        }
        if (singular == 0) {
            result.append("s");
        }
        result.append(".\n");
    }


    // Example usage (can be removed for library use)
    public static void main(String[] args) {
        NumberConverter converter = new NumberConverter(true);
        System.out.println(converter.convert(1234567));
        System.out.println(converter.convert(123.456));
        System.out.println(converter.convert(-9876543210L));
        System.out.println(converter.convert("11111111111111111111111111111111111111111111111111111111111111111")); // Test MAXNUM

        NumberConverter lConverter = new NumberConverter(true);
        System.out.println(lConverter.convert(123));
        System.out.println(lConverter.convert(0.5)); //test fractions
        System.out.println(lConverter.convert(new BigDecimal("123456789012345678901234567890")));
    }
}