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package de.hysky.skyblocker.utils;
import it.unimi.dsi.fastutil.ints.Int2ObjectLinkedOpenHashMap;
import it.unimi.dsi.fastutil.ints.Int2ObjectMap;
import it.unimi.dsi.fastutil.ints.Int2ObjectMaps;
import org.jetbrains.annotations.NotNull;
public class RomanNumerals {
private static final Int2ObjectMap<String> ROMAN_NUMERALS = Int2ObjectMaps.unmodifiable(new Int2ObjectLinkedOpenHashMap<>(
new int[]{1000, 900, 500, 400, 100, 90, 50, 40, 10, 9, 5, 4, 1},
new String[]{"M", "CM", "D", "CD", "C", "XC", "L", "XL", "X", "IX", "V", "IV", "I"}
));
private RomanNumerals() {}
private static int getDecimalValue(char romanChar) {
return switch (romanChar) {
case 'I' -> 1;
case 'V' -> 5;
case 'X' -> 10;
case 'L' -> 50;
case 'C' -> 100;
case 'D' -> 500;
case 'M' -> 1000;
default -> 0;
};
}
/**
* Checks if a string is a valid roman numeral.
* It's the caller's responsibility to clean up the string before calling this method (such as trimming it).
*
* @param romanNumeral The roman numeral to check.
* @return True if the string is a valid roman numeral, false otherwise.
* @implNote This will only check if the string contains valid roman numeral characters. It won't check if the numeral is well-formed.
*/
public static boolean isValidRomanNumeral(String romanNumeral) {
if (romanNumeral == null || romanNumeral.isEmpty()) return false;
for (int i = 0; i < romanNumeral.length(); i++) {
if (getDecimalValue(romanNumeral.charAt(i)) == 0) return false;
}
return true;
}
/**
* Converts a roman numeral to a decimal number.
*
* @param romanNumeral The roman numeral to convert.
* @return The decimal number, or 0 if the string is empty, null, or malformed.
*/
public static int romanToDecimal(String romanNumeral) {
if (romanNumeral == null || romanNumeral.isEmpty()) return 0;
romanNumeral = romanNumeral.trim().toUpperCase();
int decimal = 0;
int lastNumber = 0;
for (int i = romanNumeral.length() - 1; i >= 0; i--) {
char ch = romanNumeral.charAt(i);
int number = getDecimalValue(ch);
if (number == 0) return 0; //Malformed roman numeral
decimal = number >= lastNumber ? decimal + number : decimal - number;
lastNumber = number;
}
return decimal;
}
/**
* Converts a decimal number to a roman numeral.
*
* @param decimal The decimal number to convert.
* @return The roman numeral, or an empty string if the number is out of range.
*/
@NotNull
public static String decimalToRoman(int decimal) {
if (decimal <= 0 || decimal >= 4000) return "";
StringBuilder roman = new StringBuilder();
for (Int2ObjectMap.Entry<String> entry : ROMAN_NUMERALS.int2ObjectEntrySet()) {
int value = entry.getIntKey();
String numeral = entry.getValue();
while (decimal >= value) {
roman.append(numeral);
decimal -= value;
}
}
return roman.toString();
}
}
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