🔹 1. What is exception handling in Java?
Exception handling is a mechanism in Java used to handle runtime errors so that the normal flow of the program is not disrupted.
🔹 2. What is an exception?
An exception is an unexpected event that occurs during program execution and disrupts normal flow.
🔹 3. Difference between Error and Exception?
Error
Serious system-level issue
Cannot be handled
Example: OutOfMemoryError, StackOverflowError
Exception
Can be handled using try-catch
Example: IOException, NullPointerException
🔹** 4. Explain exception hierarchy in Java?**
Throwable
├── Error
└── Exception
├── Checked Exception
└── Unchecked Exception (RuntimeException)
🔹 5. What are checked exceptions?
Checked exceptions are compile-time exceptions that must be handled using try-catch or declared using throws.
Examples:
IOException
FileNotFoundException
SQLException
🔹 6. What are unchecked exceptions?
Unchecked exceptions occur at runtime and are not forced by the compiler.
Examples:
ArithmeticException
NullPointerException
ArrayIndexOutOfBoundsException
NumberFormatException
🔹 7. Difference between checked and unchecked exceptions?
🔹** 8. What is try-catch block?**
try contains risky code
catch handles exceptions
🔹 9. What is finally block?
The finally block always executes whether an exception occurs or not. It is used for cleanup operations.
🔹 10. Difference between throw and throws?
🔹 11. What is throw keyword?
Used to manually create an exception.
throw new ArithmeticException("Error");
🔹 12. What is throws keyword?
Used to declare exceptions in method signature and delegate handling to caller.
void read() throws IOException
🔹 13. Why do we use throws?
To inform the caller that a method may generate a checked exception.
🔹 14. Can we handle exceptions without try-catch?
Yes, using throws, but it delegates responsibility to the caller and may cause runtime crash if not handled.
🔹** 15. What happens if exception is not handled?**
Program terminates abnormally and JVM prints stack trace.
🔹 16. What is stack trace?
A stack trace shows the sequence of method calls that led to an exception, helping in debugging.
🔹 17. Can we have multiple catch blocks?
Yes, but each catch must handle a different exception type.
🔹** 18. Can finally block be skipped?**
Generally no — it always executes, except in cases like:
System.exit()
JVM crash
🔹 19. Can we throw multiple exceptions using throw?
No, throw can throw only one exception at a time.
🔹 20. Real-world use of exception handling?
Used in:
File handling
Database operations
API calls
Input validation
Network communication
⭐ BONUS INTERVIEW ONE-LINERS
🔥 Checked = compiler forces handling
🔥 Unchecked = programming mistake
🔥 throw = create exception
🔥 throws = declare exception
🔥 finally = always executes
🔥 try-catch = handles runtime failure
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