Suspending Functions & Modifiers

Suspending functions in Kotlin are special functions that can be paused and resumed later without blocking the thread. They can only be called from another suspending function or within a coroutine.

Example 1: Simple Delay

suspend fun printMessage() {
    println("Task started")
    delay(1000)
    println("Task finished after 1 second")
}

GlobalScope.launch {
    printMessage()
}

Output:
Task started
Task finished after 1 second

Example 2: Using suspend function in coroutine

suspend fun fetchData(): String {
    delay(2000)
    return "Data fetched successfully"
}

GlobalScope.launch {
    val result = fetchData()
    println(result)
}

Output:
Data fetched successfully (after 2 seconds delay)

Example 3: Sequential suspending calls

suspend fun taskOne() {
    println("Task 1 started")
    delay(1000)
    println("Task 1 finished")
}

suspend fun taskTwo() {
    println("Task 2 started")
    delay(1000)
    println("Task 2 finished")
}

GlobalScope.launch {
    taskOne()
    taskTwo()
}

Output:
Task 1 started
Task 1 finished
Task 2 started
Task 2 finished

Example 4: Running Multiple Coroutines Concurrently

private val TAG: String = "KOTLINFUN"

override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    setContentView(R.layout.activity_main2)

    CoroutineScope(Dispatchers.Main).launch {
        task1()
    }

    CoroutineScope(Dispatchers.Main).launch {
        task2()
    }
}

suspend fun task1() {
    Log.d(TAG, "STARTING TASK 1")
    delay(1000)
    Log.d(TAG, "ENDING TASK 1")
}

suspend fun task2() {
    Log.d(TAG, "STARTING TASK 2")
    delay(2000)
    Log.d(TAG, "ENDING TASK 2")
}