SupervisorJob for independent failure in Kotlin - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is SupervisorJob in Kotlin coroutines?

SupervisorJob is a special kind of job that allows child coroutines to fail independently without cancelling their siblings.

beginner

How does SupervisorJob differ from a regular Job in Kotlin?

In a regular Job, if one child coroutine fails, all siblings are cancelled. With SupervisorJob, one child's failure does not affect others.

beginner

Why use SupervisorJob in a coroutine scope?

Use SupervisorJob when you want child coroutines to run independently so that failure in one does not stop others from running.

intermediate

What happens to the parent coroutine when a child fails under SupervisorJob?

The parent coroutine does not get cancelled automatically when a child fails under SupervisorJob. It continues running.

intermediate

Show a simple Kotlin example using SupervisorJob where one child fails but others continue.

val supervisor = SupervisorJob()
val scope = CoroutineScope(Dispatchers.Default + supervisor)

scope.launch {
  delay(100)
  throw Exception("Child 1 failed")
}
scope.launch {
  delay(200)
  println("Child 2 completed")
}

Output:<br>Child 2 completed

What does SupervisorJob allow in Kotlin coroutines?

A Child coroutines fail independently without cancelling siblings

B All child coroutines cancel together on any failure

C It cancels the parent coroutine on any child failure

D It prevents any coroutine from failing

SupervisorJob allows child coroutines to fail independently without cancelling their siblings.

If a child coroutine fails under a regular Job, what happens?

A Only the failed child is cancelled

B Nothing happens

C The parent coroutine continues unaffected

D All sibling coroutines are cancelled

Under a regular Job, failure in one child cancels all siblings.

Which of these is true about SupervisorJob?

A It cancels the parent on child failure

B It allows siblings to continue after a child failure

C It prevents any coroutine from starting

D It is the default job for all coroutines

SupervisorJob allows siblings to continue running even if one child fails.

How do you create a coroutine scope with SupervisorJob?

A CoroutineScope(Dispatchers.Default + Job())

B CoroutineScope(Dispatchers.Default)

C CoroutineScope(Dispatchers.Default + SupervisorJob())

D CoroutineScope(SupervisorJob())

You combine a dispatcher with SupervisorJob() to create the scope.

What will be printed in this code?<br>

val scope = CoroutineScope(Dispatchers.Default + SupervisorJob())
scope.launch { throw Exception("Fail") }
scope.launch { println("Hello") }

A Hello

B Nothing, all coroutines cancelled

C Exception message printed

D Hello and Exception message printed

With SupervisorJob, the second child prints "Hello" despite the first child's failure.

Explain how SupervisorJob helps manage failures in child coroutines.

Think about what happens when one child fails but others keep working.

Describe how to create a coroutine scope that uses SupervisorJob and why you would do that.

Focus on the syntax and the benefit of independent failure.