feat: Add Expression3 class to calculate surface area and volume of a cuboid

Add a program that:
- Takes length, breadth, and height as input from the user
- Calculates the total surface area using the formula: 2(lb + lh + bh)
- Computes the volume using the formula: l × b × h
- Demonstrates integer input handling and geometric formula application in Java.

Author: Someshdiwan

Section5OperatorExpression/src/Expression3.java

@@ -1,13 +1,13 @@
 import java.util.Scanner;
 
 public class Expression3 {
-    public static void main(String args[]){
+    public static void main(String args[]) {
         Scanner sc = new Scanner(System.in);
 
-        int length, breadth, height;
-        int totalArea,volume;
+        int length, breadth, height; //taken from input.
+        int totalArea,volume; //calculate and store the output into the variable.
 
-        System.out.print("Enter Length breadth and Height ");
+        System.out.print("Enter Length breadth and Height: ");
 
         length=sc.nextInt();
         breadth=sc.nextInt();
@@ -20,4 +20,4 @@ public static void main(String args[]){
         System.out.println("Total area: "+ totalArea);
         System.out.println("Volume: "+volume);
     }
-}
+}