From 18f6f8c30ae993406cfac4774817b0313956161f Mon Sep 17 00:00:00 2001
From: Piotr Idzik <65706193+vil02@users.noreply.github.com>
Date: Mon, 23 Sep 2024 10:33:55 +0200
Subject: [PATCH] fix: handle Null Dereference in `RomanToInteger` (#5461)

---
 .inferconfig                                        |  1 -
 .../thealgorithms/conversions/RomanToInteger.java   | 13 ++++++-------
 .../conversions/RomanToIntegerTest.java             |  9 +++++++++
 3 files changed, 15 insertions(+), 8 deletions(-)

diff --git a/.inferconfig b/.inferconfig
index 93bd1c355..e7af307a6 100644
--- a/.inferconfig
+++ b/.inferconfig
@@ -1,7 +1,6 @@
 {
     "report-block-list-path-regex": [
         "src/main/java/com/thealgorithms/ciphers/a5/CompositeLFSR.java",
-        "src/main/java/com/thealgorithms/conversions/RomanToInteger.java",
         "src/main/java/com/thealgorithms/datastructures/crdt/GCounter.java",
         "src/main/java/com/thealgorithms/datastructures/crdt/PNCounter.java",
         "src/main/java/com/thealgorithms/datastructures/graphs/KahnsAlgorithm.java",
diff --git a/src/main/java/com/thealgorithms/conversions/RomanToInteger.java b/src/main/java/com/thealgorithms/conversions/RomanToInteger.java
index cf2d41458..1934e9b26 100644
--- a/src/main/java/com/thealgorithms/conversions/RomanToInteger.java
+++ b/src/main/java/com/thealgorithms/conversions/RomanToInteger.java
@@ -19,6 +19,10 @@ public final class RomanToInteger {
         }
     };
 
+    private static int romanSymbolToInt(final char symbol) {
+        return ROMAN_TO_INT.computeIfAbsent(symbol, c -> { throw new IllegalArgumentException("Unknown Roman symbol: " + c); });
+    }
+
     // Roman Number = Roman Numerals
 
     /**
@@ -39,10 +43,10 @@ public final class RomanToInteger {
 
             if (prev != ' ') {
                 // checking current Number greater than previous or not
-                newPrev = ROMAN_TO_INT.get(prev) > newPrev ? ROMAN_TO_INT.get(prev) : newPrev;
+                newPrev = romanSymbolToInt(prev) > newPrev ? romanSymbolToInt(prev) : newPrev;
             }
 
-            int currentNum = ROMAN_TO_INT.get(c);
+            int currentNum = romanSymbolToInt(c);
 
             // if current number greater than prev max previous then add
             if (currentNum >= newPrev) {
@@ -57,9 +61,4 @@ public final class RomanToInteger {
 
         return sum;
     }
-
-    public static void main(String[] args) {
-        int sum = romanToInt("MDCCCIV");
-        System.out.println(sum);
-    }
 }
diff --git a/src/test/java/com/thealgorithms/conversions/RomanToIntegerTest.java b/src/test/java/com/thealgorithms/conversions/RomanToIntegerTest.java
index c51986f2a..f03563971 100644
--- a/src/test/java/com/thealgorithms/conversions/RomanToIntegerTest.java
+++ b/src/test/java/com/thealgorithms/conversions/RomanToIntegerTest.java
@@ -1,6 +1,7 @@
 package com.thealgorithms.conversions;
 
 import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
 
 import org.junit.jupiter.api.Test;
 
@@ -10,5 +11,13 @@ public class RomanToIntegerTest {
     public void testRomanToInteger() {
         assertEquals(1994, RomanToInteger.romanToInt("MCMXCIV"));
         assertEquals(58, RomanToInteger.romanToInt("LVIII"));
+        assertEquals(1804, RomanToInteger.romanToInt("MDCCCIV"));
+    }
+
+    @Test
+    void testRomanToIntegerThrows() {
+        assertThrows(IllegalArgumentException.class, () -> RomanToInteger.romanToInt("Z"));
+        assertThrows(IllegalArgumentException.class, () -> RomanToInteger.romanToInt("MZI"));
+        assertThrows(IllegalArgumentException.class, () -> RomanToInteger.romanToInt("MMMO"));
     }
 }