BAEL-9402: Calculate the Difference of Two Angle Measures in Java (#18875)

Co-authored-by: Nikhil Bhargava <[email protected]>

Author: nikhil1980

algorithms-modules/algorithms-numeric/src/main/java/com/baeldung/algorithms/twoanglesdifference/AngleDifferenceCalculator.java

@@ -0,0 +1,64 @@
+/**
+ * Package to host code for calculating three types of angle difference
+ */
+package com.baeldung.algorithms.twoanglesdifference;
+
+public class AngleDifferenceCalculator {
+
+    /**
+     * Normalizes an angle to be within the range [0, 360).
+     *
+     * @param angle The angle in degrees.
+     * @return The normalized angle.
+     */
+    public static double normalizeAngle(double angle) {
+        return (angle % 360 + 360) % 360;
+    }
+
+    /**
+     * Calculates the absolute difference between two angles.
+     *
+     * @param angle1 The first angle in degrees.
+     * @param angle2 The second angle in degrees.
+     * @return The absolute difference in degrees.
+     */
+    public static double absoluteDifference(double angle1, double angle2) {
+        return Math.abs(angle1 - angle2);
+    }
+
+    /**
+     * Calculates the shortest difference between two angles.
+     *
+     * @param angle1 The first angle in degrees.
+     * @param angle2 The second angle in degrees.
+     * @return The shortest difference in degrees (0 to 180).
+     */
+    public static double shortestDifference(double angle1, double angle2) {
+        double diff = absoluteDifference(normalizeAngle(angle1), normalizeAngle(angle2));
+        return Math.min(diff, 360 - diff);
+    }
+
+    /**
+     * Calculates the signed shortest difference between two angles.
+     * A positive result indicates counter-clockwise rotation, a negative result indicates clockwise.
+     *
+     * @param angle1 The first angle in degrees.
+     * @param angle2 The second angle in degrees.
+     * @return The signed shortest difference in degrees (-180 to 180).
+     */
+    public static double signedShortestDifference(double angle1, double angle2) {
+        double normalizedAngle1 = normalizeAngle(angle1);
+        double normalizedAngle2 = normalizeAngle(angle2);
+        double diff = normalizedAngle2 - normalizedAngle1;
+
+        if (diff > 180) {
+            return diff - 360;
+        } else if (diff < -180) {
+            return diff + 360;
+        } else {
+            return diff;
+        }
+    }
+}
+
+

algorithms-modules/algorithms-numeric/src/test/java/com/baeldung/algorithms/twoanglesdifference/AngleDifferenceCalculatorTest.java

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+/**
+ * Package to host JUnit Test code for AngleDifferenceCalculator Class
+ */
+package com.baeldung.algorithms.twoanglesdifference;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import org.junit.jupiter.api.Test;
+
+
+
+class AngleDifferenceCalculatorTest {
+
+    private static final double EPSILON = 0.0001;
+
+    @Test
+    void whenNormalizingAngle_thenReturnsCorrectRange() {
+        assertEquals(90, AngleDifferenceCalculator.normalizeAngle(450), EPSILON);
+        assertEquals(30, AngleDifferenceCalculator.normalizeAngle(390), EPSILON);
+        assertEquals(330, AngleDifferenceCalculator.normalizeAngle(-30), EPSILON);
+        assertEquals(0, AngleDifferenceCalculator.normalizeAngle(360), EPSILON);
+    }
+
+    @Test
+    void whenCalculatingAbsoluteDifference_thenReturnsCorrectValue() {
+        assertEquals(100, AngleDifferenceCalculator.absoluteDifference(10, 110), EPSILON);
+        assertEquals(290, AngleDifferenceCalculator.absoluteDifference(10, 300), EPSILON);
+        assertEquals(30, AngleDifferenceCalculator.absoluteDifference(-30, 0), EPSILON);
+    }
+
+    @Test
+    void whenCalculatingShortestDifference_thenReturnsCorrectValue() {
+        assertEquals(100, AngleDifferenceCalculator.shortestDifference(10, 110), EPSILON);
+        assertEquals(70, AngleDifferenceCalculator.shortestDifference(10, 300), EPSILON);
+        assertEquals(30, AngleDifferenceCalculator.shortestDifference(-30, 0), EPSILON);
+        assertEquals(0, AngleDifferenceCalculator.shortestDifference(360, 0), EPSILON);
+    }
+
+    @Test
+    void whenCalculatingSignedShortestDifference_thenReturnsCorrectValue() {
+        assertEquals(100, AngleDifferenceCalculator.signedShortestDifference(10, 110), EPSILON);
+        assertEquals(-70, AngleDifferenceCalculator.signedShortestDifference(10, 300), EPSILON);
+        assertEquals(30, AngleDifferenceCalculator.signedShortestDifference(-30, 0), EPSILON);
+        assertEquals(70, AngleDifferenceCalculator.signedShortestDifference(300, 10), EPSILON);
+    }
+}
+