feat: add FileInputStream demo to read file byte by byte

WHAT:
- Implemented a simple file I/O example using `FileInputStream`.
- Opened `Demo1.txt` and read data one byte at a time.
- Printed each byte as a character to the console.
- Ensured proper resource cleanup by explicitly calling `fin.close()`.
- Wrapped in try-catch to handle file not found and I/O errors gracefully.

KEY LEARNINGS:
1. FileInputStream
   - A byte stream for reading raw bytes from a file.
   - Works for both text and binary data (images, audio, video).
   - `fin.read()` → returns an int [0–255] or -1 (EOF).

2. Conversion and Loop
   - `(char)i` converts numeric byte value to character for printing.
   - While loop continues until EOF is reached (-1).

3. Exception Handling
   - Prevents crashes if file path is wrong or I/O issues occur.
   - Closing stream (`fin.close()`) is essential to free system resources.

4. Best Practices
   - Prefer `try-with-resources` (Java 7+) → auto-closes file stream.
   - Use `FileReader`/`BufferedReader` for text files (encoding-aware).
   - Use `FileInputStream` for binary files (e.g., PDFs, images).

REAL-LIFE APPLICATIONS:
- Reading configuration or log files.
- Streaming binary data (images, audio, video).
- Implementing custom parsers for protocols or file formats.
- Low-level utilities (e.g., checksum calculators, file encryption).

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

Author: Someshdiwan

Section23JavaIOStreams/DemoCodes/TXT Files/Demo1.txt

@@ -1 +1 @@
-//This Java program reads a text file character by character using FileInputStream and prints its content to the console.
+This Java program reads a text file character by character using FileInputStream and prints its content to the console.

Section23JavaIOStreams/DemoCodes/src/Demo1.java

@@ -1,28 +1,54 @@
 import java.io.FileInputStream;
-public class Demo1
-{
+public class Demo1 {
     public static void main(String args[]){
-        try
-        {
-            FileInputStream fin=new FileInputStream("C://Users//somes//Downloads//NoteApp//JavaEvolution-Learning-Growing-Mastering\\Section23JavaIOStreams\\DemoCodes\\TXT Files\\Demo1.txt");
-            int i=0;
+        try {
+            FileInputStream fin = new FileInputStream
+                            ("/Users/somesh/Java SE/JavaEvolution-Learning-Growing-Mastering/Section23JavaIOStreams/DemoCodes/TXT Files/Demo1.txt");
 
-            while((i=fin.read())!=-1)
-            {
+            int i=0;
+            while((i=fin.read())!=-1) {
                 System.out.print((char)i);
             }
-
-            /*
-                    Reads the file one byte at a time.
-                    fin.read() returns an int representing the byte value. It returns -1 when the end of the file (EOF) is reached.
-                    (char)i converts the byte into a character, and it prints it to the console.
-                    So, this part prints the entire content of the file.
-            */
             fin.close();
         }
-        catch(Exception e)
-        {
+        catch(Exception e) {
             System.out.println(e);
         }
     }
 }
+
+/*
+Reads the file one byte at a time.
+fin.read() returns an int representing the byte value. It returns -1 when the end of the file (EOF) is reached.
+(char)i converts the byte into a character, and it prints it to the console.
+So, this part prints the entire content of the file.
+
+1. FileInputStream:
+   - Ye ek byte stream hai jo file ke andar ka data byte by byte read karta hai.
+   - Mostly text files, image files, audio/video streams ke liye use hota hai.
+
+2. Code Explanation:
+   - `FileInputStream fin = new FileInputStream("path");`
+     → Ye file ko open karta hai given path par.
+   - `fin.read()` ek-ek byte return karta hai (0-255 integer value).
+   - Jab end of file (EOF) aata hai, to -1 return hota hai.
+   - `(char)i` cast karke hum us integer ko character me convert karke print karte hain.
+   - `fin.close()` resource (file handle) free kar deta hai.
+
+3. Loop Working:
+   - while loop tab tak chalega jab tak file khatam nahi hoti.
+   - Har byte → char me cast → console par print.
+
+4. Exception Handling:
+   - Agar file nahi mili (FileNotFoundException) ya koi I/O error aaya
+     → catch block run hoga aur error print karega.
+
+5. Output:
+   - File me jo bhi likha hai, wahi console par as-it-is print ho jaayega.
+
+- Always close the stream (`fin.close()`) warna resource leak ho sakta hai.
+- Better approach: try-with-resources (Java 7+), jisme close automatic ho jaata hai.
+- Text files ke liye `FileReader` / `BufferedReader` zyada convenient hote hain
+  (kyunki wo character streams hai, encoding friendly).
+- FileInputStream mainly tab use hota hai jab tumhe binary data (images, audio, pdf) read karna ho.
+*/