feat: Demonstrate checked exceptions vs runtime errors in method chaining

WHAT the code does:
- Defines class CheckedException with three static methods:
  - fun1():
    - Commented code shows creation of FileInputStream with "My.txt".
    - Would throw a **checked exception** (FileNotFoundException), which must be handled with try–catch or declared with throws.
  - fun2(): calls fun1().
  - fun3(): recursively calls itself without a base case, leading to infinite recursion and eventually StackOverflowError.
- main(): calls fun3(), causing StackOverflowError at runtime.

WHY this matters:
- Shows difference between **checked exceptions** and **unchecked errors**:
  - Checked exceptions:
    - Caught or declared at compile-time (e.g., FileNotFoundException, SQLException).
    - Example: FileInputStream requires handling since file might not exist.
  - Unchecked exceptions/errors:
    - Occur at runtime, not enforced by compiler (e.g., NullPointerException, StackOverflowError).
    - fun3 demonstrates uncontrolled recursion leading to StackOverflowError.
- Highlights how compiler enforces handling for checked exceptions but allows recursive calls that may crash at runtime.

HOW it works:
1. If FileInputStream in fun1 were uncommented:
   - Compilation fails unless code is wrapped in try–catch or method signature declares `throws FileNotFoundException`.
2. fun3():
   - Calls itself infinitely.
   - JVM stack memory fills up.
   - Throws StackOverflowError (unchecked, subclass of Error).
3. main():
   - Directly triggers fun3(), causing program crash at runtime.

Tips and gotchas:
- Always handle checked exceptions with try–catch or propagate them with throws.
- Recursion requires a base case to terminate; otherwise stack overflow occurs.
- StackOverflowError cannot be caught meaningfully for recovery; fix logic instead.
- Checked exceptions = compile-time obligation; unchecked exceptions = runtime responsibility.

Use-cases / analogies:
- Checked exceptions: like airport security requiring you to handle your luggage before boarding (must handle before runtime).
- Unchecked errors: like falling asleep while driving — compiler doesn’t stop you, but program (car) crashes at runtime.

Short key: java exceptions checked-vs-unchecked fileinputstream stackoverflow recursion.

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

Author: Someshdiwan

Section18ExceptionHandling/src/CheckedException.java

@@ -1,22 +1,22 @@
 import java.io.FileInputStream;
 
-public class CheckedException
-{
+public class CheckedException {
     static void fun1()
     {
         /*
         Checked Exception FileInputStream f1=new FileInputStream("My.txt");
         */
     }
-    static void fun2()
-    {
+
+    static void fun2() {
         fun1();
     }
-    static void fun3()
-    {
+
+    static void fun3() {
         fun3();
     }
+
     public static void main(String[] args) {
         fun3();
     }
-}
+}