feat(constructors): add example demonstrating parameterized constructor and instance initialization

What
- Introduced `Constructors` class with two instance attributes:
  - `label` (String) to represent a descriptive identifier.
  - `number` (double) to represent a numeric value.
- Implemented a parameterized constructor:
  - Accepts `valueOfLabel` and `valueOfNumber` as arguments.
  - Initializes `label` and `number` fields at the time of object creation.
- Added `main` method:
  - Creates an instance `thing = new Constructors("HIS", 1.2)`.
  - Prints the assigned label using `System.out.println`.

Why
- Demonstrates how Java constructors provide a way to initialize objects at creation.
- Reinforces the distinction between **constructors** and **methods**:
  - Constructor has the same name as the class, no return type.
  - Automatically invoked when an object is created.
- Encourages writing constructors for encapsulating initialization logic instead of using setter methods later.

Logic
1. Fields declared: `label` and `number`.
2. Constructor `Constructors(String, double)`:
   - Binds the incoming arguments to the instance attributes.
3. Inside `main`:
   - `new Constructors("HIS", 1.2)` allocates memory and calls the constructor.
   - Constructor assigns `"HIS"` to `label` and `1.2` to `number`.
   - `thing.label` prints `"HIS"`.

Real-life applications
- Parameterized constructors are widely used to ensure **valid state** of objects at creation:
  - Example: Creating `User(name, email)` ensures a user always has required info.
  - Example: Creating `BankAccount(accountNo, balance)` enforces initialization rules.
- Reduces risk of uninitialized objects and enforces **immutability** when combined with `final` fields.

Notes
- If no constructor is defined, Java provides a default no-arg constructor.
- Once a parameterized constructor is defined, the default constructor is no longer provided unless explicitly added.
- Good practice: use constructors for mandatory fields, setters for optional ones.

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

Author: Someshdiwan

JAVA8/ConstructorReference/src/Constructors.java renamed to Java 8 Crash Course/Functional Interface/Static Methods/src/Constructors.java

@@ -1,22 +1,18 @@
-public class Constructors
-{
-    //Instance attributes//
+public class Constructors {
+    //Instance attributes
     public String label;
     public double number;
 
-    //Constructor//
-    public Constructors(String valueOfLabel, double valueOfNumber)
-    {
+    //Constructor
+    public Constructors(String valueOfLabel, double valueOfNumber) {
         label = valueOfLabel;
         number = valueOfNumber;
     }
 
-    public static void main(String[] args)
-    {
+    public static void main(String[] args) {
         //create an object and assign the values at the same time
         Constructors thing = new Constructors("HIS", 1.2);
 
-        //let's see if it worked
         System.out.println("My thing's label is " + thing.label);
     }
 }