Fixed sonar, added test

Author: javadev

src/main/java/g3401_3500/s3448_count_substrings_divisible_by_last_digit/Solution.java

@@ -97,7 +97,7 @@ private long countDivisibilityBy8(String s, int j) {
         }
         int num3 = (s.charAt(j - 2) - '0') * 100 + (s.charAt(j - 1) - '0') * 10 + 8;
         int num2 = (s.charAt(j - 1) - '0') * 10 + 8;
-        return (num3 % 8 == 0 ? j - 1 : 0) + (num2 % 8 == 0 ? 1 : 0) + 1;
+        return (num3 % 8 == 0 ? j - 1 : 0) + (num2 % 8 == 0 ? 1 : 0) + 1L;
     }
 
     private long countDivisibilityBy7(int j, int[] p7, long[][] freq7, int[] inv7) {

src/test/java/g3401_3500/s3448_count_substrings_divisible_by_last_digit/SolutionTest.java

@@ -20,4 +20,9 @@ void countSubstrings2() {
     void countSubstrings3() {
         assertThat(new Solution().countSubstrings("1010101010"), equalTo(25L));
     }
+
+    @Test
+    void countSubstrings4() {
+        assertThat(new Solution().countSubstrings("4"), equalTo(1L));
+    }
 }