SAM conversions for Java interfaces in Kotlin - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a Runnable using SAM conversion.

Kotlin

val runnable = Runnable { println([1]) }
runnable.run()

Drag options to blanks, or click blank then click option'

Aprintln("Hello from SAM")

B"Hello from SAM"

CHello from SAM

Drun()

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting to put quotes around the string.

Trying to call println inside the lambda incorrectly.

The Runnable interface's single abstract method run() takes no arguments and returns Unit. Using SAM conversion, we provide a lambda that prints the string. The string must be quoted.

2fill in blank

medium

Complete the code to create a Comparator using SAM conversion that compares integers.

Kotlin

val comparator = Comparator<Int> { a, b -> a [1] b }
println(comparator.compare(5, 3))

Drag options to blanks, or click blank then click option'

A/

B+

C*

D-

Attempts:

3 left

💡 Hint

Common Mistakes

Using addition instead of subtraction.

Using multiplication or division which do not give correct comparison.

Comparator's compare method returns a negative, zero, or positive number depending on order. Subtracting b from a gives the correct comparison result.

3fill in blank

hard

Fix the error in the SAM conversion for ActionListener.

Kotlin

val listener = ActionListener { e -> println(e.[1]) }

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AactionCommand

BgetActionCommand()

CgetAction()

Dcommand

Attempts:

3 left

💡 Hint

Common Mistakes

Using the Java getter method syntax instead of Kotlin property.

Using incorrect method names.

In Kotlin, Java getter methods can be accessed as properties. So getActionCommand() becomes actionCommand.

4fill in blank

hard

Fill both blanks to create a Thread using SAM conversion and start it.

Kotlin

val thread = Thread([1])
thread.[2]()

Drag options to blanks, or click blank then click option'

A{ println("Running in thread") }

Bstart

Crun

DThread()

Attempts:

3 left

💡 Hint

Common Mistakes

Calling run() instead of start() on the thread.

Not providing a lambda as Runnable.

Thread constructor accepts a Runnable, which can be provided as a lambda. To run the thread, call start(), not run().

5fill in blank

hard

Fill all three blanks to create a Timer with delay 1000, an ActionListener using SAM conversion, and start the timer.

Kotlin

val timer = Timer([1], [2])
timer.[3]()

Drag options to blanks, or click blank then click option'

A1000

B{ e -> println("Timer fired") }

Cstart

Dstop

Attempts:

3 left

💡 Hint

Common Mistakes

Using stop() instead of start() to run the timer.

Not providing the correct delay value.

Timer constructor takes delay in milliseconds and an ActionListener. The listener can be a lambda. To run the timer, call start().