scala.concurrent.Future#sequence
Useful for reducing many Futures into a single Future.

收集 Future 执行结果，通过 foreach  取出收集结果并进行后续处理



import java.time.LocalDateTime
import scala.concurrent.ExecutionContext.Implicits.global
import scala.concurrent.Future

object FutureSequenceDemo {
  def main(args: Array[String]) {
    val f1 = Future {
      Thread.sleep(2000)
      println("Future1.time=" + LocalDateTime.now().toString())
      println("Future1.currentThread=" + Thread.currentThread().getName)
      "a"
    }
    val f2 = Future {
      Thread.sleep(1000)
      println("Future2.time=" + LocalDateTime.now().toString())
      println("Future2.currentThread=" + Thread.currentThread().getName)
      "b"
    }

    //  Future[List[String]]
    val f3 = Future.sequence(List(f1, f2))
    f3.foreach(println)
    println("time1=" + LocalDateTime.now())
    println("f3=" + f3)
    println("time2=" + LocalDateTime.now())

    Thread.sleep(3000)
    println("f3.2=" + f3)
  }
}




time1=2022-02-14T12:32:27.126
f3=Future(< not completed >)
time2=2022-02-14T12:32:27.129
Future1.time=2022-02-14T12:32:28.056
Future1.currentThread=ForkJoinPool-1-worker-13
Future2.time=2022-02-14T12:32:29.055
Future2.currentThread=ForkJoinPool-1-worker-11
List(a, b)
f3.2=Future(Success(List(a, b)))