feat: Add ParentDemo and ChildDemo with parameterized constructors and super calls

WHAT the code does:
Defines ParentDemo with two constructors:
- No-argument constructor prints "Non-Param of parent".
- Parameterized constructor prints "Param of parent <x>".
Defines ChildDemo extending ParentDemo with three constructors:
- No-argument constructor prints "Non-Param of child".
- Single-argument constructor prints "Param of child".
- Two-argument constructor calls super(x) then prints "2 param of child <y>".
Defines ParametrisedConstructors with main():
- Creates ChildDemo object using two-argument constructor.

WHY this matters:
Demonstrates **constructor chaining** in inheritance:
- Child constructors can explicitly call parent constructors using super().
Reinforces the role of super for invoking parent behavior.
Shows how object construction flows from superclass → subclass.

HOW it works:
ChildDemo c = new ChildDemo(10, 20):
- Calls ChildDemo(int x,int y).
- Executes super(x) → ParentDemo(int x) prints "Param of parent 10".
- Then prints "2 param of child 20".
If no super(...) is explicitly called, Java automatically inserts a no-argument super().

Tips and gotchas:
Always call super() explicitly when parent doesn’t have a no-argument constructor.
@ comments clarify that super refers to the immediate superclass.
Typo in comment: "supper is a keyword" → should be "super is a keyword".
Class and method names follow Java conventions, though ParametrisedConstructors could be renamed ConstructorChainingDemo for clarity.

Use-cases:
Educational demonstration of parameterized constructors and constructor chaining.
Prepares for real-world use where subclasses must initialize parent state.
Foundation for understanding initialization order in OOP.

Short key: class-parentdemo childdemo constructor-chaining super.

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

Author: Someshdiwan

Section12Inheritance/src/ParametrisedConstructors.java

@@ -1,39 +1,34 @@
-class ParentDemo
-{
-    ParentDemo()
-    {
+class ParentDemo {
+    ParentDemo() {
         System.out.println("Non-Param of parent");
     }
-    ParentDemo(int x)
-    {
+
+    ParentDemo(int x) {
         System.out.println("Param of parent "+x);
     }
 }
 
-class ChildDemo extends ParentDemo
-{
-    ChildDemo()
-    {
+class ChildDemo extends ParentDemo {
+    ChildDemo() {
         System.out.println("Non-Param of child");
     }
-    ChildDemo(int y)
-    {
+
+    ChildDemo(int y) {
         System.out.println("Param of child");
     }
-    ChildDemo(int x,int y)
-    {
+
+    ChildDemo(int x,int y) {
         super(x);
-        //this will caalled the super class.
-        // super is keyword which refer to the super class.
+        // this will call the super class.
+        // supper is a keyword that refers to the super class.
         System.out.println("2 param of child "+y);
 
     }
 }
-public class ParametrisedConstructors
-{
-    public static void main(String[] args)
-    {
+
+public class ParametrisedConstructors {
+    public static void main(String[] args) {
         ChildDemo c=new ChildDemo(10,20);
-        //we call parameterized constructer of super class.
+        //we call parameterized constructor of super class.
     }
 }