Google Guava synchronizedQueue initialization error in Scala

Question

I am trying to initialize Guava synchronizedQueue in Scala for performence benchmarking.

class TestSynchronizedQueueJavaPTS {
  private var assignedQForTest : java.util.Queue[Int] = null;
  private var syncQueue   : java.util.Queue[Int] = null;

  def create(DS_Type : String) : java.util.concurrent.ConcurrentLinkedQueue[Int] ={
     DS_Type match{
       case "syncQueue" =>
         syncQueue = com.google.common.collect.Queues.synchronizedQueue(com.google.common.collect.MinMaxPriorityQueue.[Int]create());
         assignedQForTest = syncQueue;
     }   
     assignedQForTest
  }
}

But I am getting this error:

identifier expected but '[' found.

Source of error: .[Int] part.

I have the equivalent Java Code which is working perfectly fine without any error:

import java.util.Queue;
import com.google.common.collect.MinMaxPriorityQueue;
import com.google.common.collect.Queues;

public class test {
    public static void main(String[] args) {
        Queue<Integer> queue = Queues.synchronizedQueue(MinMaxPriorityQueue.<Integer>create());
        queue.add(15);
        queue.add(63);
        queue.add(20);
        System.out.println (queue.poll());
        System.out.println (queue.poll());
    }
}

Dave L. · Accepted Answer · 2016-03-28 17:03:05Z

1

The type param should go after the method name like below. Then, there is another compilation error since Scala's Int is not Comparable. I changed it to Integer to get around that, but maybe you will prefer a different way of resolving that particular issue.

  private var assignedQForTest : java.util.Queue[Integer] = null;
  private var syncQueue   : java.util.Queue[Integer] = null;

  def create(DS_Type : String) : java.util.Queue[Integer] ={
     DS_Type match{
       case "syncQueue" =>
         syncQueue = com.google.common.collect.Queues.synchronizedQueue(com.google.common.collect.MinMaxPriorityQueue.create[Integer]());
         assignedQForTest = syncQueue;
     }   
     assignedQForTest
  }

answered Mar 28, 2016 at 17:03

Dave L.

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2 Comments

Pranay Over a year ago

Sorrz, it does not work. Gives the following error:

◾type arguments [Int] conform to the bounds of none of the overloaded alternatives of value create: [E <: Comparable[E]](x$1: Iterable[_ <: E])com.google.common.collect.MinMaxPriorityQueue[E] <and> [E <: Comparable[E]]()com.google.common.collect.MinMaxPriorityQueue[E] ◾wrong number of type parameters for overloaded method value create with alternatives: [E <: Comparable[E]](x$1: Iterable[_ <: E])com.google.common.collect.MinMaxPriorityQueue[E] <and> [E <: Comparable[E]]()com.google.common.collect.MinMaxPriorityQueue[E]

Dave L. Over a year ago

@Pranay You didn't make the second change I mentioned -- changing Int to Integer. Also, I'm just returning a Queue. Just copy/paste the code and check it out

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