Advanced Exception Handling

Multi-catch & Custom Hierarchy

💡 Multi-catch is one security guard who handles different kinds of troublemakers (exceptions) at a single gate — no need to build a separate gate for each.

A single catch block can catch multiple exception types using "|": catch (IOException | SQLException e).

You can build your own hierarchy of custom exceptions — like a base AppException, extended into a specific PaymentFailedException — this organizes errors in large projects.

try {
  riskyOperation();
} catch (IOException | SQLException e) {
  System.out.println("Handled: " + e.getMessage());
}

class AppException extends Exception {}
class PaymentFailedException extends AppException {}

🧯

Multi-catch is one security guard who handles different kinds of troublemakers (exceptions) at a single gate — no need to build a separate gate for each.

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Koi bhi class jo AutoCloseable interface implement karti hai (FileReader, Scanner, database Connection, etc.) try-with-resources mein use ho sakti hai. try(...) ke andar resource declare karo, aur block khatam hote hi (chahe normally ya exception se) close() automatically call ho jaata hai — manually finally mein close() likhने ki zaroorat khatam.

Java 9+ mein resource ko try() ke bahar bhi declare kar sakte ho (agar wo effectively final ho) aur sirf naam try() mein likh sakte ho — thoda cleaner syntax.

try (Scanner sc = new Scanner(System.in)) {
  String input = sc.nextLine();
} // sc.close() automatically ho gaya

// Multiple resources bhi ek saath:
try (FileReader fr = new FileReader("a.txt"); FileWriter fw = new FileWriter("b.txt")) {
  // dono automatically close honge, reverse order mein
}

Custom exception banate waqt: meaningful naam do (InsufficientBalanceException, na ki MyException ya Exception1), Exception ya RuntimeException extend karo (checked vs unchecked decide karke — is subtopic ke last point mein detail hai), aur ek constructor do jo message accept kare aur super(message) call kare.

Extra fields bhi add kar sakte ho custom exception mein — jaise InsufficientBalanceException mein "shortfallAmount" field, taaki catch karne wala code us extra info ko use kar sake.

class InsufficientBalanceException extends RuntimeException {
  final double shortfall;
  InsufficientBalanceException(String message, double shortfall) {
    super(message);
    this.shortfall = shortfall;
  }
}

Kabhi-kabhi ek exception doosre exception ki wajah se aati hai — "cause" ke through original exception ko wrap kar sakte ho, taaki original root-cause ki info khoye nahi (stack trace mein "Caused by:" dikhta hai). new CustomException("msg", originalException) jaisa pattern — dusra argument "cause" hai.

try {
  readFile();
} catch (IOException e) {
  throw new ServiceException("File load fail hua", e); // cause preserved
}

Checked exception (jo Exception extend kare, RuntimeException nahi) use karo jab caller ko *zaroor* handle karna chahiye, aur recovery possible ho (jaise file not found — retry ya alternate path try kar sakte ho). Compiler force karta hai ki ya to try-catch karo, ya throws se aage pass karo.

Unchecked (RuntimeException) use karo programming errors ke liye jo bugs hain, recovery normally nahi hoti (jaise invalid argument pass karna, null pointer) — inhe har jagah try-catch karna majboori nahi hai, compiler force nahi karta.

	Checked	Unchecked (RuntimeException)
Compiler force karta hai handle karna?	Haan	Nahi
Example	IOException, SQLException	NullPointerException, IllegalArgumentException
Kab use karein	Recoverable, external problems	Programming bugs, logic errors

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Code10x

Advanced Exception Handling

try-with-resources — Deep Dive

Custom Exception — Best Practices

Exception Chaining

Checked vs Unchecked — Kab Kaunsa