给定这个Java:
Queue.DeclareOk queueDeclare(String queue, boolean durable, boolean exclusive, boolean autoDelete,
Map<String, Object> arguments) throws IOException;
从 Scala 传递这样的null
是合法的:
channel.queueDeclare(inputQueueName, true, false, true, null)
在 Scala 中传递空地图的声明是什么?这:
channel.queueDeclare(inputQueueName, true, false, true, Map[String, Object]())
结果:
found : scala.collection.immutable.Map[String,Object]
required: java.util.Map[String,Object]
channel.queueDeclare(inputQueueName, true, false, true, Map[String,Object]())
和:
channel.queueDeclare(inputQueueName, true, false, true, java.util.HashMap[String,Object]())
结果:
object java.util.HashMap is not a value
import scala.collection.JavaConverters._
val emptyMap = Map.empty[String, Object].asJava
// java.util.Map[String, Object]
channel.queueDeclare(inputQueueName, true, false, true, emptyMap)
或:
channel.queueDeclare(inputQueueName, true, false, true, new java.util.HashMap[String, Object]())
// ^ add new here
new java.util.HashMap[String, Object]
(不带括号(也有效。