注意 import scala.concurrent.ExecutionContext.Implicits.global
不导入 Future创建会报错
No implicit arguments of type: ExecutionContext

需要显示 提供 scala.concurrent.ExecutionContext

object Future extends scala.AnyRef {
  def apply[T](body : => T)(implicit executor : scala.concurrent.ExecutionContext) : scala.concurrent.Future[T]  
  
object ExecutionContext extends scala.AnyRef {
  def fromExecutor(e : java.util.concurrent.Executor) : scala.concurrent.ExecutionContextExecutor  
  
trait ExecutionContextExecutor extends scala.AnyRef with scala.concurrent.ExecutionContext with java.util.concurrent.Executor {


// 创建线程池 用于 future执行
val executor = Executors.newFixedThreadPool(3)
val executionContext = ExecutionContext.fromExecutor(executor)


// 在指定的线程池中运行
val future3 = Future {
  Thread.sleep(1000)
  List("a3", "b3", "c3")
}(executionContext)
    


import java.util.concurrent._
import scala.concurrent.ExecutionContext.Implicits.global
import scala.concurrent.duration.Duration
import scala.concurrent.{Await, ExecutionContext, Future}

object FutureDemo {

  // 创建线程池 用于 future执行
  val executor = Executors.newFixedThreadPool(3)
  val executionContext = ExecutionContext.fromExecutor(executor)

  def main(args: Array[String]) {
    val future = Future {
      getList()
    }
    val future2 = Future {
      Thread.sleep(2000)
      List("a2", "b2", "c2")
    }

    // 在指定的线程池中运行
    val future3 = Future {
      Thread.sleep(1000)
      List("a3", "b3", "c3")
    }(executionContext)

    println("future=" + future)
    println("future2=" + future2)

    // for 多行 用 大括号
    val list3Future = for {
      list1 <- future
      list2 <- future2
      list3 = list1 ++ list2
    } yield {
      // list1 ++ list2
      list3
    }
    println("list3Future=" + list3Future)

    // 等待执行完成
    var result = Await.result(list3Future, Duration.Inf)
    println("result=" + result)
    println("list3Future.2=" + list3Future)
    println("list3Future.isCompleted=" + list3Future.isCompleted)

    list3Future.foreach(println)

    println("future3=" + future3)


  }

  def getList(): List[String] = {
    Thread.sleep(1000)
    List("a", "b", "c")
  }

}



也可以这样

val list3Future = for {
  list1 <- future
  list2 <- future2
} yield {
  list1 ++ list2
}


完整代码
https://gitee.com/dyyx/hellocode/blob/master/demo/scala/scalademo/src/main/java/demo2/FutureDemo.scala




 scala Future和Promise