About Question com.enthuware.ets.scjp.v6.2.82 :

[pushpull]

Code: Select all

import java.util.*;
class Request { }
class RequestCollector{
    //1 : Insert declaration here
    
    public synchronized void addRequest(Request r){
	container.add(r);
    }
    public synchronized Request getRequestToProcess(){
	return container.poll();
    }
}

What can be inserted at //1?

In the explanation there is

(...)the use of poll() method indicates that it must be a Queue. Both LinkedList and PriorityQueue classes implement Queue interface.

So why the answer

Code: Select all

Queue container = new PriorityQueue();

is wrong?
and those two are good?

Code: Select all

Queue<Request> container = new LinkedList<Request>();
LinkedList container = new LinkedList();

[admin]

In case of Queue container = new PriorityQueue(); the container is not typed to Queue<Request>. So container.poll() will not satisfy the return type of the method.

[pushpull]

But the LinkedList container = new LinkedList(); isn't typed either to LinkedList<Request>, so why there is no problem here?

[admin]

You are right. This should also be a wrong option.
Fixed.

thank you for your feedback!
Paul.