Timeout with withTimeout in Kotlin - Mini Project: Build & Apply

Timeout with withTimeout

📖 Scenario: Imagine you are making a simple program that waits for a task to finish, but you don't want to wait forever. You want to stop waiting if it takes too long.

🎯 Goal: You will build a Kotlin program that uses withTimeout to stop waiting after a set time.

📋 What You'll Learn

Create a suspend function that simulates a long task

Set a timeout duration using withTimeout

Run the task inside withTimeout

Handle the timeout exception and print a message

💡 Why This Matters

🌍 Real World

Timeouts are useful when waiting for slow tasks like network calls or user input, so your program doesn't freeze or wait forever.

💼 Career

Many jobs require handling timeouts to keep apps responsive and avoid crashes, especially in mobile and backend development.

1

Create a suspend function to simulate a long task

Write a suspend function called longTask that waits for 3000 milliseconds using delay(3000).

Kotlin

# Write the suspend function longTask with delay(3000)
// Your code here

Need a hint?

Use suspend fun to create a function that can pause. Use delay(3000) to wait 3 seconds.

2

Set a timeout duration using withTimeout

Create a val timeoutMillis and set it to 2000L to represent 2000 milliseconds timeout.

Kotlin

import kotlinx.coroutines.delay

suspend fun longTask() {
    delay(3000)
}

// Create a val timeoutMillis and set it to 2000L
// Your code here

Need a hint?

Use val timeoutMillis = 2000L to set the timeout to 2 seconds.

3

Run the task inside withTimeout

Write a suspend function called runWithTimeout that uses withTimeout(timeoutMillis) to run longTask().

Kotlin

import kotlinx.coroutines.delay
import kotlinx.coroutines.withTimeout

suspend fun longTask() {
    delay(3000)
}

val timeoutMillis = 2000L

// Write suspend fun runWithTimeout that runs longTask inside withTimeout(timeoutMillis)
// Your code here

Need a hint?

Use withTimeout(timeoutMillis) { longTask() } inside the new suspend function.

4

Handle timeout exception and print result

Write a main function that calls runBlocking and inside it calls runWithTimeout(). Catch TimeoutCancellationException and print "Timeout happened!". If no timeout, print "Task completed".

Kotlin

import kotlinx.coroutines.delay
import kotlinx.coroutines.withTimeout
import kotlinx.coroutines.runBlocking
import kotlinx.coroutines.TimeoutCancellationException

suspend fun longTask() {
    delay(3000)
}

val timeoutMillis = 2000L

suspend fun runWithTimeout() {
    withTimeout(timeoutMillis) {
        longTask()
    }
}

// Write main function with runBlocking
// Call runWithTimeout inside try-catch
// Print "Timeout happened!" if timeout exception
// Print "Task completed" if no exception
// Your code here

Need a hint?

Use try { runWithTimeout() } and catch (e: TimeoutCancellationException) to print the timeout message.