added implemetation and test

Signed-off-by: Emmanuel Mireku Omari <[email protected]>

Author: Emmanuel-Omari01

core-java-modules/core-java-lang-math-4/src/main/java/com/baeldung/math/percentagedifferecebetweentwonumbers/PercentageDifferenceBetweenTwoNumbers.java

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+package com.baeldung.math.percentagedifferecebetweentwonumbers;
+
+public class PercentageDifferenceBetweenTwoNumbers {
+  public static double calculatePercentageDifference(double V1, double V2) {
+    double average = (V1 + V2) / 2;
+    if (average == 0) {
+      throw new IllegalArgumentException("The average of V1 and V2 cannot be zero.");
+    }
+    return Math.abs((V1 - V2) / average) * 100;
+  }
+}

core-java-modules/core-java-lang-math-4/src/test/java/com/baeldung/PercentageDifferenceBetweenTwoNumbersTest/PercentageDifferenceBetweenTwoNumbersTest.java

@@ -0,0 +1,84 @@
+package com.baeldung.PercentageDifferenceBetweenTwoNumbersTest;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+import com.baeldung.math.percentagedifferecebetweentwonumbers.PercentageDifferenceBetweenTwoNumbers;
+import org.junit.jupiter.api.Test;
+
+public class PercentageDifferenceBetweenTwoNumbersTest {
+
+  @Test
+  void calculatePercentageDifferenceBetweenTwoNumbers() {
+    double V1 = 50.0;
+    double V2 = 70.0;
+    double expected = 33.33;
+    double result = PercentageDifferenceBetweenTwoNumbers.calculatePercentageDifference(V1, V2);
+    assertEquals(expected, result, 0.01, "Percentage difference should be correctly calculated.");
+  }
+
+  @Test
+  void whenV1AndV2AreEqual_thenPercentageDifferenceIsZero() {
+    double V1 = 50.0;
+    double V2 = 50.0;
+    double expected = 0.0;
+    double result = PercentageDifferenceBetweenTwoNumbers.calculatePercentageDifference(V1, V2);
+    assertEquals(
+        expected, result, "Percentage difference should be zero when both values are equal.");
+  }
+
+  @Test
+  void whenV1IsGreaterThanV2_thenCalculateCorrectPercentageDifference() {
+    double V1 = 70.0;
+    double V2 = 50.0;
+    double expected = 33.33;
+    double result = PercentageDifferenceBetweenTwoNumbers.calculatePercentageDifference(V1, V2);
+    assertEquals(expected, result, 0.01, "Percentage difference should be correctly calculated.");
+  }
+
+  @Test
+  void whenV2IsGreaterThanV1_thenCalculateCorrectPercentageDifference() {
+    double V1 = 50.0;
+    double V2 = 70.0;
+    double expected = 33.33;
+    double result = PercentageDifferenceBetweenTwoNumbers.calculatePercentageDifference(V1, V2);
+    assertEquals(expected, result, 0.01, "Percentage difference should be correctly calculated.");
+  }
+
+  @Test
+  void whenOneValueIsZero_thenCalculateCorrectPercentageDifference() {
+    double V1 = 0.0;
+    double V2 = 50.0;
+    double expected = 200.0;
+    double result = PercentageDifferenceBetweenTwoNumbers.calculatePercentageDifference(V1, V2);
+    assertEquals(
+        expected,
+        result,
+        "Percentage difference should be correctly calculated when one value is zero.");
+  }
+
+  @Test
+  void whenAverageIsZero_thenThrowIllegalArgumentException() {
+    double V1 = -50.0;
+    double V2 = 50.0;
+    assertThrows(
+        IllegalArgumentException.class,
+        () -> {
+          PercentageDifferenceBetweenTwoNumbers.calculatePercentageDifference(V1, V2);
+        },
+        "Should throw IllegalArgumentException when the average of V1 and V2 is zero.");
+  }
+
+  @Test
+  void whenV1AndV2AreSwapped_thenPercentageDifferenceIsSame() {
+    double V1 = 70.0;
+    double V2 = 50.0;
+    double expecgit ted = PercentageDifferenceBetweenTwoNumbers.calculatePercentageDifference(V1, V2);
+    double result = PercentageDifferenceBetweenTwoNumbers.calculatePercentageDifference(V2, V1);
+    assertEquals(
+        expected,
+        result,
+        0.01,
+        "Percentage difference should be the same when V1 and V2 are swapped.");
+  }
+}