refactor: cleanup DudeneyNumber (#5156)

Author: vil02

pmd-exclude.properties

@@ -41,7 +41,6 @@ com.thealgorithms.dynamicprogramming.WineProblem=UselessParentheses
 com.thealgorithms.maths.BinomialCoefficient=UselessParentheses
 com.thealgorithms.maths.Complex=UselessParentheses
 com.thealgorithms.maths.DistanceFormulaTest=UnnecessaryFullyQualifiedName
-com.thealgorithms.maths.DudeneyNumber=UselessParentheses
 com.thealgorithms.maths.FibonacciJavaStreamsTest=BigIntegerInstantiation
 com.thealgorithms.maths.Gaussian=UselessParentheses
 com.thealgorithms.maths.GcdSolutionWrapper=UselessParentheses

src/main/java/com/thealgorithms/maths/DudeneyNumber.java

@@ -11,28 +11,18 @@ private DudeneyNumber() {
     }
 
     // returns True if the number is a Dudeney number and False if it is not a Dudeney number.
-    public static boolean isDudeney(int n) {
+    public static boolean isDudeney(final int n) {
+        if (n <= 0) {
+            throw new IllegalArgumentException("Input must me positive.");
+        }
         // Calculating Cube Root
-        int cube_root = (int) (Math.round((Math.pow(n, 1.0 / 3.0))));
+        final int cube_root = (int) Math.round(Math.pow(n, 1.0 / 3.0));
         // If the number is not a perfect cube the method returns false.
         if (cube_root * cube_root * cube_root != n) {
             return false;
         }
-        int sum_of_digits = 0; // Stores the sums of the digits of the entered number
-        int temp = n; // A temporary variable to store the entered number
-        // Loop to calculate the sum of the digits.
-        while (temp > 0) {
-            // Extracting the Last digit of the number
-            int rem = temp % 10;
-
-            // Calculating the sum of digits.
-            sum_of_digits += rem;
-
-            // Removing the last digit
-            temp /= 10;
-        }
 
         // If the cube root of the number is not equal to the sum of its digits, we return false.
-        return cube_root == sum_of_digits;
+        return cube_root == SumOfDigits.sumOfDigits(n);
     }
 }

src/test/java/com/thealgorithms/maths/DudeneyNumberTest.java

@@ -1,18 +1,28 @@
 package com.thealgorithms.maths;
 
 import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertThrows;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 
-import org.junit.jupiter.api.Test;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.CsvSource;
 
 class DudeneyNumberTest {
+    @ParameterizedTest
+    @CsvSource({"1", "512", "4913", "5832", "17576", "19683"})
+    void positiveDudeneyBase10Power3(final int n) {
+        assertTrue(DudeneyNumber.isDudeney(n));
+    }
 
-    @Test
-    void isDudeney() {
-        final int validDudeneyNumber = 512;
-        final int invalidDudeneyNumber = 125;
+    @ParameterizedTest
+    @CsvSource({"2", "19", "21", "125", "27", "343", "729", "19682", "19684"})
+    void negativeDudeneyBase10Power3(final int n) {
+        assertFalse(DudeneyNumber.isDudeney(n));
+    }
 
-        assertTrue(() -> DudeneyNumber.isDudeney(validDudeneyNumber));
-        assertFalse(() -> DudeneyNumber.isDudeney(invalidDudeneyNumber));
+    @ParameterizedTest
+    @CsvSource({"0", "-1"})
+    void throwsInputLessThanOne(final int n) {
+        assertThrows(IllegalArgumentException.class, () -> DudeneyNumber.isDudeney(n));
     }
 }