Merge pull request eugenp#16833 from 3ga01/percentage-diff-of-two-numbers

Percentage Difference Between  Two Numbers

Author: acerasoni

core-java-modules/core-java-lang-math-4/src/main/java/com/baeldung/math/percentdiffbetweentwonumbers/PercentDiffBetweenTwoNumbers.java

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+package com.baeldung.math.percentdiffbetweentwonumbers;
+
+public class PercentDiffBetweenTwoNumbers {
+
+    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/math/percentdiffbetweentwonumberstest/PercentDiffBetweenTwoNumbersUnitTest.java

@@ -0,0 +1,73 @@
+package com.baeldung.math.percentdiffbetweentwonumberstest;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+
+import org.junit.jupiter.api.Test;
+
+import com.baeldung.math.percentdiffbetweentwonumbers.PercentDiffBetweenTwoNumbers;
+
+class PercentDiffBetweenTwoNumbersUnitTest {
+
+    @Test
+    void whenCalculatePercentageDifferenceBetweenTwoNumbers_thenCorrectResult() {
+        double v1 = 50.0;
+        double v2 = 70.0;
+        double expected = 33.33;
+        double result = PercentDiffBetweenTwoNumbers.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 = PercentDiffBetweenTwoNumbers.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 = PercentDiffBetweenTwoNumbers.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 = PercentDiffBetweenTwoNumbers.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 = PercentDiffBetweenTwoNumbers.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, () -> PercentDiffBetweenTwoNumbers.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 expected = PercentDiffBetweenTwoNumbers.calculatePercentageDifference(v1, v2);
+        double result = PercentDiffBetweenTwoNumbers.calculatePercentageDifference(v2, v1);
+        assertEquals(expected, result, 0.01, "Percentage difference should be the same when v1 and v2 are swapped.");
+    }
+}