feat(StackDemo1): add interactive stack input and save contents to file

What
- Added StackDemo1 class.
- Used Scanner to take user input.
- Created a Stack<Integer>.
- Asked user how many elements to push.
- Iteratively read integers and pushed them onto the stack.
- Printed the stack contents.
- Implemented saveStackToFile() method:
  - Used BufferedWriter + FileWriter to write each stack element to a file, one per line.
  - Wrapped file writing in try-with-resources for safe closure.
- Closed Scanner after input.

Why
- Demonstrates interactive usage of Stack with user input.
- Shows how to persist stack contents into a file.
- Combines collections (Stack) with I/O (BufferedWriter) for practical example.

How
- User prompted for n.
- For loop reads n integers via sc.nextInt() and pushes into stack.
- After input, printed stack.
- saveStackToFile() iterates stack, writes each value with newline.
- File saved to hardcoded path.

Logic
- Inputs: integer count n and stack elements.
- Outputs:
  - Printed stack contents.
  - Saved stack elements to text file.
- Flow:
  1. Prompt for size.
  2. Read elements, push to stack.
  3. Print stack contents.
  4. Write contents to file.
- Edge cases:
  - Non-integer input throws InputMismatchException.
  - File path invalid or lacking permissions → IOException caught and error message shown.
  - Empty stack still creates empty file.
- Complexity:
  - Stack push O(1) per element.
  - File write O(n).
- Concurrency: Stack is synchronized but Scanner/FileWriter are not thread-safe here.

Real-life applications
- Capturing runtime stack input from users.
- Persisting stack state for later retrieval or debugging.
- Useful template for combining data structures with file I/O.

Notes
- Hardcoded file path may fail across systems; should use relative paths or configurable paths.
- Prefer try-with-resources for Scanner as well to ensure closure.
- In modern code, ArrayDeque often replaces Stack, but demo illustrates legacy class + file persistence nicely.

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

Author: Someshdiwan

Section25CollectionFramework/src/ListDemo/SatckDemo/InputStacks.java renamed to Section 25 Collections Frameworks/List Interface/Vector/Stack/src/StackDemo1.java

@@ -1,16 +1,16 @@
-package ListDemo.SatckDemo;
-
 import java.io.BufferedWriter;
 import java.io.FileWriter;
 import java.io.IOException;
 import java.util.Scanner;
 import java.util.Stack;
 
-public class InputStacks {
+public class StackDemo1 {
     public static void main(String[] args) {
         Scanner sc = new Scanner(System.in);
+
+        // Input Stacks
         Stack<Integer> stack = new Stack<>();
-        System.out.print("Enter the number of elements to push: ");
+        System.out.print("Enter the number of elements you want to store inside the stack: ");
 
         int n = sc.nextInt(); // Take the number of elements as input
 
@@ -22,20 +22,18 @@ public static void main(String[] args) {
         System.out.println("\nStack contents: " + stack); // Print stack contents
 
         // Save stack data to a file
-        saveStackToFile(stack, "C://Users//somes//Downloads//JAVA SE\\Section25CollectionFramework\\src\\ListDemo\\SatckDemo\\stack_data.txt");
+        saveStackToFile(stack, "/Users/somesh/Java SE/JavaEvolution-Learning-Growing-Mastering/Section 25 Collections Frameworks/List Interface/Vector/Stack/src/Output.txt");
         sc.close();
     }
 
     public static void saveStackToFile(Stack<Integer> stack, String filename) {
-        try (BufferedWriter writer = new BufferedWriter(new FileWriter(filename)))
-        {
-            for (int item : stack)
-            {
+        try (BufferedWriter writer = new BufferedWriter(new FileWriter(filename))) {
+            for (int item : stack) {
                 writer.write(item + "\n"); // Write each stack element on a new line
             }
             System.out.println("Stack contents saved to " + filename);
         } catch (IOException e) {
             System.out.println("Error writing to file: " + e.getMessage());
         }
     }
-}
+}