feat(constructor-reference): demonstrate using Supplier with Example::new for lazy object creation

What
- Added `Example` class with a no-argument constructor that prints a message when invoked.
- Added `ConstructorReference` class to show:
  - Declaring a `Supplier<Example>` functional interface.
  - Assigning the constructor reference `Example::new` to it.
  - Using `supplier.get()` to trigger actual object creation.

Why
- Shows how constructor references integrate seamlessly with functional interfaces like `Supplier<T>`.
- Demonstrates **lazy instantiation**: object is not created until `get()` is explicitly invoked.
- Reinforces that method/constructor references are syntactic sugar for lambdas, improving readability.

Logic
1. `Supplier<Example> supplier = Example::new;`
   - Binds the no-arg constructor of `Example` to the `Supplier` functional interface.
   - Equivalent lambda: `() -> new Example()`.
2. `Example ex = supplier.get();`
   - Calls `get()`, which internally executes `new Example()`.
   - Prints `"Example constructor called!"` because of the constructor side-effect.

Real-life applications
- Lazy initialization of heavy resources (e.g., database connections, file readers).
- Factories for object creation in dependency injection frameworks.
- Stream pipelines where new objects are created on-demand without verbose lambdas.

Notes
- `Supplier<T>` is a built-in functional interface from `java.util.function`.
- Constructor reference works when the constructor signature matches the functional interface’s abstract method:
  - Here, `Supplier<T>` has `T get()` → matches `Example()` constructor.
- Key benefit: **cleaner and more expressive code** than explicitly writing lambdas or anonymous classes.

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

Author: Someshdiwan

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

@@ -5,12 +5,12 @@ class Example {
         System.out.println("Example constructor called!");
     }
 }
-public class ConstructorReference {
+public class ConstructorReferenceDmo {
     public static void main(String[] args) {
         // Using a constructor reference
         Supplier<Example> supplier = Example::new;
 
         // Calling get() will invoke the constructor
         Example ex = supplier.get();
     }
-}
+}