refactor: EulersFunction

Author: alxkm

src/main/java/com/thealgorithms/others/EulersFunction.java

@@ -1,24 +1,32 @@
 package com.thealgorithms.others;
 
 /**
- * @brief utility class for <a href="https://en.wikipedia.org/wiki/Euler%27s_totient_function">Euler's totient function</a>
+ * Utility class for computing
+ * <a href="https://en.wikipedia.org/wiki/Euler%27s_totient_function">Euler's totient function</a>.
  */
 public final class EulersFunction {
     private EulersFunction() {
     }
 
+    /**
+     * Validates that the input is a positive integer.
+     *
+     * @param n the input number to validate
+     * @throws IllegalArgumentException if {@code n} is non-positive
+     */
     private static void checkInput(int n) {
         if (n <= 0) {
             throw new IllegalArgumentException("n must be positive.");
         }
     }
 
     /**
-     * @brief computes the value of Euler's totient function for given input
-     * @details has time complexity of O(sqrt(n))
-     * @param n the input
-     * @exception IllegalArgumentException n is non-positive
-     * @return the value of Euler's totient function for the input
+     * Computes the value of Euler's totient function for a given input.
+     * This function has a time complexity of O(sqrt(n)).
+     *
+     * @param n the input number
+     * @return the value of Euler's totient function for the given input
+     * @throws IllegalArgumentException if {@code n} is non-positive
      */
     public static int getEuler(int n) {
         checkInput(n);

src/test/java/com/thealgorithms/others/EulersFunctionTest.java

@@ -3,37 +3,32 @@
 import static org.junit.jupiter.api.Assertions.assertEquals;
 import static org.junit.jupiter.api.Assertions.assertThrows;
 
-import java.util.HashMap;
-import org.junit.jupiter.api.Test;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.Arguments;
+import org.junit.jupiter.params.provider.MethodSource;
+
+import java.util.stream.Stream;
 
 class EulersFunctionTest {
-    @Test
-    public void testGetEuler() {
-        HashMap<Integer, Integer> testCases = new HashMap<>();
-        testCases.put(1, 1);
-        testCases.put(2, 1);
-        testCases.put(3, 2);
-        testCases.put(4, 2);
-        testCases.put(5, 4);
-        testCases.put(6, 2);
-        testCases.put(10, 4);
-        testCases.put(21, 12);
-        testCases.put(69, 44);
-        testCases.put(47, 46);
-        testCases.put(46, 22);
-        testCases.put(55, 40);
-        testCases.put(34, 16);
-        testCases.put(20, 8);
-        testCases.put(20, 8);
-        testCases.put(1024, 512);
-
-        for (final var tc : testCases.entrySet()) {
-            assertEquals(tc.getValue(), EulersFunction.getEuler(tc.getKey()));
-        }
+
+    @ParameterizedTest
+    @MethodSource("provideNumbersForGetEuler")
+    void testGetEuler(int input, int expected) {
+        assertEquals(expected, EulersFunction.getEuler(input));
+    }
+
+    @ParameterizedTest
+    @MethodSource("provideInvalidNumbersForGetEuler")
+    void testGetEulerThrowsExceptionForNonPositiveInput(int input) {
+        assertThrows(IllegalArgumentException.class, () -> EulersFunction.getEuler(input));
     }
 
-    @Test
-    public void testGetEulerThrowsExceptionForNonPositiveInput() {
-        assertThrows(IllegalArgumentException.class, () -> EulersFunction.getEuler(0));
+    private static Stream<Arguments> provideNumbersForGetEuler() {
+        return Stream.of(Arguments.of(1, 1), Arguments.of(2, 1), Arguments.of(3, 2), Arguments.of(4, 2), Arguments.of(5, 4), Arguments.of(6, 2), Arguments.of(10, 4), Arguments.of(21, 12), Arguments.of(69, 44), Arguments.of(47, 46), Arguments.of(46, 22), Arguments.of(55, 40), Arguments.of(34, 16), Arguments.of(20, 8), Arguments.of(1024, 512));
+    }
+
+    private static Stream<Arguments> provideInvalidNumbersForGetEuler() {
+        return Stream.of(Arguments.of(0), Arguments.of(-1), Arguments.of(-10));
     }
 }
+