Exception handling in coroutines in Kotlin - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of try-catch blocks in Kotlin coroutines?

They are used to catch and handle exceptions that occur inside a coroutine, preventing the coroutine from crashing the program.

intermediate

How does CoroutineExceptionHandler help in exception handling?

It is a special coroutine context element that catches uncaught exceptions in coroutines and allows centralized handling of those exceptions.

intermediate

What happens if an exception is thrown in a child coroutine launched with launch?

The exception is propagated to the parent coroutine and can cancel the parent and its other children unless handled properly.

advanced

Why should exceptions in async coroutines be handled differently?

Because async coroutines return a Deferred result, exceptions are thrown only when await() is called, so handling should be done around await().

advanced

What is the role of supervisorScope in exception handling?

It allows child coroutines to fail independently without cancelling their siblings or the parent, helping to isolate exceptions.

Which coroutine builder propagates exceptions immediately to its parent?

A async

B launch

C runBlocking

D supervisorScope

The launch builder propagates exceptions immediately to its parent coroutine.

Where should you handle exceptions when using async coroutines?

A Exceptions are ignored in <code>async</code>

B Inside the coroutine block

C In <code>CoroutineExceptionHandler</code>

D When calling <code>await()</code>

Exceptions in async coroutines are thrown when await() is called, so handling should be done there.

What does CoroutineExceptionHandler NOT catch?

A Exceptions in <code>async</code> coroutines before <code>await()</code>

B Exceptions in <code>runBlocking</code>

C Uncaught exceptions in coroutines

D Exceptions in <code>launch</code> coroutines

CoroutineExceptionHandler does not catch exceptions in async coroutines before await() is called.

What is the effect of using supervisorScope?

A Allows child coroutines to fail independently

B Cancels all child coroutines on any failure

C Ignores all exceptions silently

D Runs coroutines sequentially

supervisorScope lets child coroutines fail without cancelling siblings or the parent.

Which statement about exception handling in coroutines is TRUE?

A Exceptions in coroutines always crash the whole application

B Exceptions in <code>async</code> are ignored

C Exceptions in <code>launch</code> are propagated immediately

D <code>try-catch</code> cannot be used inside coroutines

Exceptions in launch coroutines are propagated immediately to the parent.

Explain how exception handling differs between launch and async coroutines in Kotlin.

Think about when exceptions become visible in each coroutine builder.

Describe the purpose and benefits of using supervisorScope for exception handling in coroutines.

Consider how failures affect other coroutines inside the scope.