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109 lines
4.1 KiB
Java
109 lines
4.1 KiB
Java
package com.thealgorithms.conversions;
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import java.util.Map;
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/**
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* A utility class to convert integers to their English word representation.
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*
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* <p>The class supports conversion of numbers from 0 to 2,147,483,647
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* (the maximum value of a 32-bit signed integer). It divides the number
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* into groups of three digits (thousands, millions, billions, etc.) and
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* translates each group into words.</p>
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*
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* <h2>Example Usage</h2>
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* <pre>
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* IntegerToEnglish.integerToEnglishWords(12345);
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* // Output: "Twelve Thousand Three Hundred Forty Five"
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* </pre>
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*
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* <p>This class uses two maps:</p>
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* <ul>
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* <li>BASE_NUMBERS_MAP: Holds English words for numbers 0-20, multiples of 10 up to 90, and 100.</li>
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* <li>THOUSAND_POWER_MAP: Maps powers of 1000 (e.g., Thousand, Million, Billion).</li>
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* </ul>
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*/
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public final class IntegerToEnglish {
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private static final Map<Integer, String> BASE_NUMBERS_MAP = Map.ofEntries(Map.entry(0, ""), Map.entry(1, "One"), Map.entry(2, "Two"), Map.entry(3, "Three"), Map.entry(4, "Four"), Map.entry(5, "Five"), Map.entry(6, "Six"), Map.entry(7, "Seven"), Map.entry(8, "Eight"), Map.entry(9, "Nine"),
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Map.entry(10, "Ten"), Map.entry(11, "Eleven"), Map.entry(12, "Twelve"), Map.entry(13, "Thirteen"), Map.entry(14, "Fourteen"), Map.entry(15, "Fifteen"), Map.entry(16, "Sixteen"), Map.entry(17, "Seventeen"), Map.entry(18, "Eighteen"), Map.entry(19, "Nineteen"), Map.entry(20, "Twenty"),
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Map.entry(30, "Thirty"), Map.entry(40, "Forty"), Map.entry(50, "Fifty"), Map.entry(60, "Sixty"), Map.entry(70, "Seventy"), Map.entry(80, "Eighty"), Map.entry(90, "Ninety"), Map.entry(100, "Hundred"));
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private static final Map<Integer, String> THOUSAND_POWER_MAP = Map.ofEntries(Map.entry(1, "Thousand"), Map.entry(2, "Million"), Map.entry(3, "Billion"));
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private IntegerToEnglish() {
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}
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/**
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* Converts numbers less than 1000 into English words.
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*
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* @param number the integer value (0-999) to convert
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* @return the English word representation of the input number
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*/
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private static String convertToWords(int number) {
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int remainder = number % 100;
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StringBuilder result = new StringBuilder();
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if (remainder <= 20) {
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result.append(BASE_NUMBERS_MAP.get(remainder));
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} else if (BASE_NUMBERS_MAP.containsKey(remainder)) {
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result.append(BASE_NUMBERS_MAP.get(remainder));
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} else {
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int tensDigit = remainder / 10;
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int onesDigit = remainder % 10;
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String tens = BASE_NUMBERS_MAP.getOrDefault(tensDigit * 10, "");
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String ones = BASE_NUMBERS_MAP.getOrDefault(onesDigit, "");
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result.append(tens);
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if (ones != null && !ones.isEmpty()) {
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result.append(" ").append(ones);
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}
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}
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int hundredsDigit = number / 100;
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if (hundredsDigit > 0) {
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if (result.length() > 0) {
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result.insert(0, " ");
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}
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result.insert(0, String.format("%s Hundred", BASE_NUMBERS_MAP.get(hundredsDigit)));
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}
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return result.toString().trim();
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}
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/**
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* Converts a non-negative integer to its English word representation.
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*
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* @param number the integer to convert (0-2,147,483,647)
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* @return the English word representation of the input number
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*/
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public static String integerToEnglishWords(int number) {
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if (number == 0) {
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return "Zero";
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}
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StringBuilder result = new StringBuilder();
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int index = 0;
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while (number > 0) {
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int remainder = number % 1000;
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number /= 1000;
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if (remainder > 0) {
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String subResult = convertToWords(remainder);
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if (!subResult.isEmpty()) {
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if (index > 0) {
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subResult += " " + THOUSAND_POWER_MAP.get(index);
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}
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if (result.length() > 0) {
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result.insert(0, " ");
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}
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result.insert(0, subResult);
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}
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}
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index++;
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}
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return result.toString().trim();
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}
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}
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