This Gist describes the Kotlin flow terminal operators .

FlowTerminalOperators.kt

fun main() {

    val flow = flow {
        delay(200)
        emit(1)

        delay(200)
        emit(2)

        delay(200)
        emit(2)
    }

    val singleFlow = flow {
        emit("Single Emitted value")
    }

    runBlocking {
        flow.collect { receivedValue ->
            println("Collect Received value 1: $receivedValue")
            /** Output :
             * Collect Received value 1: 1
             * Collect Received value 1: 2
             * Collect Received value 1: 2
             */
        }

        val itemFirst = flow.first()
        println("first() flow : $itemFirst")
        /** Output :
         * first() flow : 1
         */

        val itemLast = flow.last()
        println("last() flow : $itemLast")
        /**
         * last() flow : 2
         */

        val itemSingle = singleFlow.single()
        println("single() flow : $itemSingle") // output : single() flow : Single Emitted value
        /**
         * Exception in thread "main" java.lang.IllegalArgumentException: Flow has more than one element
         * 	at kotlinx.coroutines.flow.FlowKt__ReduceKt$single$2.emit(Reduce.kt:54)
         * 	at kotlinx.coroutines.flow.internal.SafeCollectorKt$emitFun$1.invoke(SafeCollector.kt:11)
         * 	at kotlinx.coroutines.flow.internal.SafeCollectorKt$emitFun$1.invoke(SafeCollector.kt:11)
         * 	at kotlinx.coroutines.flow.internal.SafeCollector.emit(SafeCollector.kt:113)
         * 	at kotlinx.coroutines.flow.internal.SafeCollector.emit(SafeCollector.kt:82)
         */

        val setFLow = flow.toSet()
        println("toSet() flow : $setFLow")
        /**
         * Output :  toSet() flow : [1, 2]
         */

        val listFLow = flow.toList()
        println("toList() flow : $listFLow")
        /**
         * toList() flow : [1, 2, 2]
         */
    }
}