[Feature] Helper for Roman Numerals

src/main/java/org/betterx/bclib/util/RomanNumeral.java

@@ -0,0 +1,45 @@
+package org.betterx.bclib.util;
+
+import java.util.TreeMap;
+
+/**
+ * base on <a href="https://stackoverflow.com/questions/12967896/converting-integers-to-roman-numerals-java">...</a>
+ */
+
+public class RomanNumeral {
+    private final static TreeMap<Integer, String> LITERALS = new TreeMap<>();
+
+    private static void lazyInit() {
+        if (LITERALS.isEmpty()) {
+            LITERALS.put(1000, "M");
+            LITERALS.put(900, "CM");
+            LITERALS.put(500, "D");
+            LITERALS.put(400, "CD");
+            LITERALS.put(100, "C");
+            LITERALS.put(90, "XC");
+            LITERALS.put(50, "L");
+            LITERALS.put(40, "XL");
+            LITERALS.put(10, "X");
+            LITERALS.put(9, "IX");
+            LITERALS.put(5, "V");
+            LITERALS.put(4, "IV");
+            LITERALS.put(1, "I");
+        }
+    }
+
+    public static String toRoman(int number) {
+        lazyInit();
+        return _toRoman(number);
+    }
+
+    private static String _toRoman(int number) {
+        //there is no 0 in roman, but we need it anyway ;)
+        if (number == 0) return "0";
+        
+        int l = LITERALS.floorKey(number);
+        if (number == l) {
+            return LITERALS.get(number);
+        }
+        return LITERALS.get(l) + _toRoman(number - l);
+    }
+}