Kotlin协程await与join挂起函数异同

Kotlin协程await与join挂起函数异同

import kotlinx.coroutines.async
import kotlinx.coroutines.delay
import kotlinx.coroutines.runBlocking

fun main() {
    runBlocking {
        println("start")

        val job1 = async {
            println("1...")
            val t = (Math.random() * 999).toLong()
            delay(t)
            println("1 $t")
        }

        val job2 = async {
            println("2...")
            val t = (Math.random() * 999).toLong()
            delay(t)
            println("2 $t")
        }

        val job3 = async {
            println("3...")
            val t = (Math.random() * 999).toLong()
            delay(t)
            println("3 $t")
        }

        val r1 = job1.await()
        val r2 = job2.await()
        val r3 = job3.await()

        println("start next")
    }
}

输出：

start
1...
2...
3...
3 103
2 419
1 558
start next

Process finished with exit code 0

Kotlin协程中的await与join挂起函数，在某种程度上说，类似Java的CountDownLatch，等待任务完成后再进行下一步。await与join不同的是，await有返回值，join没有。xxx.await或者xxx.join，只要xxx这条协程运行完成，立即开始下一步。

相关：

https://blog.youkuaiyun.com/zhangphil/article/details/90758788

https://blog.youkuaiyun.com/zhangphil/article/details/147596030

https://blog.youkuaiyun.com/zhangphil/article/details/83443995

https://blog.youkuaiyun.com/zhangphil/article/details/154659832

https://blog.youkuaiyun.com/zhangphil/article/details/129270875

https://blog.youkuaiyun.com/zhangphil/article/details/132621143

https://blog.youkuaiyun.com/zhangphil/article/details/135272034