Add code for rotating a vertex around certain point (#15683)

Co-authored-by: rajatgarg <rajatgarg@adobe.com>

core-java-modules/core-java-lang-math-3/src/main/java/com/baeldung/math/rotatevertex/VertexRotation.java

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+package com.baeldung.math.rotatevertex;
+
+import java.awt.geom.AffineTransform;
+import java.awt.geom.Point2D;
+
+public class VertexRotation {
+    public static Point2D.Double usingOriginAsRotationPoint(Point2D.Double vertex, Point2D.Double rotationPoint, double angle) {
+        double translatedToOriginX = vertex.x - rotationPoint.x;
+        double translatedToOriginY = vertex.y - rotationPoint.y;
+
+        double rotatedX = translatedToOriginX * Math.cos(angle) - translatedToOriginY * Math.sin(angle);
+        double rotatedY = translatedToOriginX * Math.sin(angle) + translatedToOriginY * Math.cos(angle);
+
+        double reverseTranslatedX = rotatedX + rotationPoint.x;
+        double reverseTranslatedY = rotatedY + rotationPoint.y;
+
+        return new Point2D.Double(reverseTranslatedX, reverseTranslatedY);
+    }
+
+    public static Point2D.Double usingAffineTransform(Point2D.Double vertex, Point2D.Double rotationPoint, double angle) {
+        AffineTransform affineTransform = AffineTransform.getRotateInstance(angle, rotationPoint.x, rotationPoint.y);
+        Point2D.Double rotatedVertex = new Point2D.Double();
+        affineTransform.transform(vertex, rotatedVertex);
+        return rotatedVertex;
+    }
+}

core-java-modules/core-java-lang-math-3/src/test/java/com/baeldung/math/rotatevertex/VertexRotationUnitTest.java

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+package com.baeldung.math.rotatevertex;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import java.awt.geom.Point2D;
+
+import org.junit.jupiter.api.Test;
+
+public class VertexRotationUnitTest {
+    @Test
+    void givenRotationPoint_whenUseOrigin_thenRotateVertex() {
+        Point2D.Double vertex = new Point2D.Double(2.0, 2.0);
+        Point2D.Double rotationPoint = new Point2D.Double(0.0, 1.0);
+        double angle = Math.toRadians(45.0);
+        Point2D.Double rotatedVertex = VertexRotation.usingOriginAsRotationPoint(vertex, rotationPoint, angle);
+
+        assertEquals(0.707, rotatedVertex.getX(), 0.001);
+        assertEquals(3.121, rotatedVertex.getY(), 0.001);
+    }
+
+    @Test
+    void givenRotationPoint_whenUseAffineTransform_thenRotateVertex() {
+        Point2D.Double vertex = new Point2D.Double(2.0, 2.0);
+        Point2D.Double rotationPoint = new Point2D.Double(0.0, 1.0);
+        double angle = Math.toRadians(45.0);
+        Point2D.Double rotatedVertex = VertexRotation.usingAffineTransform(vertex, rotationPoint, angle);
+
+        assertEquals(0.707, rotatedVertex.getX(), 0.001);
+        assertEquals(3.121, rotatedVertex.getY(), 0.001);
+    }
+}