Exception Handling Interview Questions

Q1. What is the difference between checked and unchecked exceptions? Checked exceptions are verified by the compiler at compile-time and must be either handled or declared using throws. Unchecked exceptions extend RuntimeException and are not checked by the compiler.

Q2. What is the difference between `throw` and `throws`? throw is used inside a method to actually trigger a specific exception object. throws is used in a method's signature to declare that the method might produce a certain type of exception.

Q3. Does the `finally` block always execute? Yes, finally executes whether or not an exception occurred, and even if the try block contains a return statement (with rare exceptions, like if the JVM itself shuts down abruptly).

Q4. Can you have a try block without a catch block? Yes, as long as it has a finally block. A try block must be followed by at least one catch, or a finally, or both.

Q5. What is a custom exception, and why would you create one? A custom exception is a user-defined exception class, usually extending Exception or RuntimeException, created to represent a specific error condition relevant to your application's own business logic more clearly than a generic built-in exception would.

Q6. What happens if an exception is thrown but never caught? The program terminates abruptly, and the JVM prints a stack trace describing the exception and where it occurred.

Key Points to Remember

• Interviewers often ask you to trace through code involving nested try-catch-finally blocks — practice this carefully.
• Understand exactly when finally runs, even with early return statements inside try or catch.
• Be ready to explain real scenarios where you'd create a custom exception in a real project.