feat: Add Cuboid class extending RectangleDemo with super constructor chaining

WHAT the code does:
Defines RectangleDemo with:
- No-arg constructor initializing length and breadth = 1.
- Parameterized constructor initializing length and breadth with given values.
Defines Cuboid extending RectangleDemo with:
- No-arg constructor setting height = 1.
- Single-parameter constructor setting height.
- Three-parameter constructor calling super(l,b) to initialize parent fields, then setting height.
- volume(): computes length × breadth × height.
Defines SuperClassParameterisedConstructors with main():
- Creates a Cuboid using three-parameter constructor (5,3,10).
- Prints volume.

WHY this matters:
Demonstrates **constructor chaining** in inheritance:
- Child class uses super(...) to initialize parent class fields.
Shows code reuse: Cuboid builds upon RectangleDemo’s logic rather than reimplementing.
Illustrates how subclass-specific behavior (volume) builds on superclass state (length × breadth).

HOW it works:
Cuboid c = new Cuboid(5,3,10):
- Calls RectangleDemo(int l,int b) → sets length=5, breadth=3.
- Sets height=10.
- volume() = 5 × 3 × 10 = 150.
Output: 150.

Tips and gotchas:
Fields are package-private; better practice is to make them private with getters/setters for encapsulation.
volume() currently uses raw multiplication; could be refactored to reuse an area() method from RectangleDemo.
Class names are descriptive, but SuperClassParameterisedConstructors could be renamed CuboidDemo for clarity.
No validation exists for negative dimensions; in production, constructors or setters should enforce positivity.

Use-cases:
Educational demonstration of super constructor usage and inheritance.
Geometry modeling example extending from 2D shapes (rectangle) to 3D solids (cuboid).
Foundation for creating reusable shape hierarchies in object-oriented design.

Short key: class-rectangledemo cuboid super-constructor chaining.

Signed-off-by: https://github.com/Someshdiwan <[email protected]>

Author: Someshdiwan

Section12Inheritance/src/SuperClassParameterisedConstructors.java

@@ -1,53 +1,41 @@
-//Need Practice the same thing again.
-
-class RectangleDemo
-{
+class RectangleDemo {
     int length;
     int breadth;
 
-    RectangleDemo()
-    {
+    RectangleDemo() {
         length=breadth=1;
     }
-    RectangleDemo(int l,int b)
-    {
+
+    RectangleDemo(int l,int b) {
         length=l;
         breadth=b;
     }
-
 }
 
-class Cuboid extends RectangleDemo
-{
+class Cuboid extends RectangleDemo {
     int height;
 
-    Cuboid()
-    {
+    Cuboid() {
         height=1;
     }
 
-    Cuboid(int h)
-    {
+    Cuboid(int h) {
         height=h;
     }
-    Cuboid(int l,int b,int h)
-    {
+
+    Cuboid(int l,int b,int h) {
         super(l,b);
         height=h;
     }
 
-    int volume()
-    {
+    int volume() {
         return length*breadth*height;
     }
 }
 
-public class SuperClassParameterisedConstructors
-{
-    public static void main(String[] args)
-    {
+public class SuperClassParameterisedConstructors {
+    public static void main(String[] args) {
         Cuboid c=new Cuboid(5,3,10);
         System.out.println(c.volume());
     }
 }
-