Created VolumeTest.java & Fixed Bugs in Volume.java (#3682)

* Fixed functions and removed main() in Volume.java

Fixed calculation errors in volumeSphere() and volumeHemisphere() functions and removed main() and changed functions access specifier from private to public

* Created VolumeTest.java

Created VolumeTest.java JUnit Tests for Volume.java

Co-authored-by: Debasish Biswas <debasishbsws.abc@gmail.com>

src/test/java/com/thealgorithms/maths/VolumeTest.java

@@ -0,0 +1,35 @@
+package com.thealgorithms.maths;
+
+import static org.junit.jupiter.api.Assertions.*;
+import org.junit.jupiter.api.Test;
+
+public class VolumeTest {
+
+    @Test
+    public void volume() {
+
+        /* test cube */
+        assertTrue(Volume.volumeCube(7) == 343.0);
+
+        /* test cuboid */
+        assertTrue(Volume.volumeCuboid(2, 5, 7) == 70.0);
+
+        /* test sphere */
+        assertTrue(Volume.volumeSphere(7) == 1436.7550402417319);
+
+        /* test cylinder */
+        assertTrue(Volume.volumeCylinder(3, 7) == 197.92033717615698);
+
+        /* test hemisphere */
+        assertTrue(Volume.volumeHemisphere(7) == 718.3775201208659);
+
+        /* test cone */
+        assertTrue(Volume.volumeCone(3, 7) == 65.97344572538566);
+
+        /* test prism */
+        assertTrue(Volume.volumePrism(10, 2) == 20.0);
+
+        /* test pyramid */
+        assertTrue(Volume.volumePyramid(10, 3) == 10.0);
+    }
+}