Exception Handling Interview Questions

An exception is an event that disrupts the normal flow of program execution and occurs during runtime.

Errors represent serious system-level problems that applications usually cannot recover from, while Exceptions represent conditions that applications can handle.

Exceptions are categorized as checked exceptions and unchecked exceptions.

A checked exception is verified by the compiler and must be either handled or declared using the throws keyword.

An unchecked exception occurs at runtime and does not require explicit handling by the compiler.

throw is used to explicitly throw an exception, while throws is used in method signatures to declare exceptions that may occur.

A try-catch block is used to handle exceptions by enclosing risky code in a try block and handling errors in a catch block.

The finally block contains code that executes regardless of whether an exception occurs, typically used for resource cleanup.

Normally no, but it may not execute if the JVM terminates unexpectedly using System.exit() or due to a fatal system error.

A custom exception is a user-defined exception class that extends Exception or RuntimeException to represent application-specific errors.

Try-with-resources automatically closes resources that implement AutoCloseable, reducing boilerplate code and resource leaks.

The exception propagates up the call stack. If no handler is found, the JVM terminates the program and prints a stack trace.

final restricts modification, finally is used for cleanup in exception handling, and finalize was a garbage collection hook that is deprecated.

Exception propagation is the process of passing an exception from one method to its caller until it is handled.

Handle specific exceptions, avoid empty catch blocks, use custom exceptions when appropriate, log exceptions properly, and clean up resources using try-with-resources.

Name concrete APIs (collections, concurrency, streams, annotations) tied to Exception Handling. Interviewers want syntax-level clarity plus when you would reach for each feature in production.

Prefer specific checked/unchecked exceptions, wrap lower-level failures with context, and avoid empty catch blocks. For Exception Handling, decide what is recoverable vs fatal to the request thread.

JUnit 5 with Arrange-Act-Assert, Mockito for collaborators, and parameterized tests for edge cases. Keep Exception Handling logic pure where possible so tests stay fast.

Incorrect equals/hashCode break HashMap/HashSet behavior. If Exception Handling stores objects in collections, explain the contract and mutability pitfalls.

Retain only needed references, prefer streaming for large datasets, and avoid accidental caches. Relate leaks or GC pressure to a concrete Exception Handling scenario.