java BlockingQueue does not have a blocking peek?
blockingqueue, java, peek, queue
Solution
You could use a LinkedBlockingDeque and physically remove the item from the queue (using `takeLast()`) but replace it again at the end of the queue if processing fails using `putLast(E e)`. Meanwhile your "producers" would add elements to the front of the queue using `putFirst(E e)`.
You could always encapsulate this behaviour within your own `Queue` implementation and provide a `blockingPeek()` method that performs `takeLast()` followed by `putLast()` behind the scenes on the underlying `LinkedBlockingDeque`. Hence from the calling client's perspective the element is never removed from your queue.
Problem
I have a blocking queue of objects. I want to write a thread that blocks till there is a object on the queue. Similar to the functionality provided by BlockingQueue.take(). However, since I do not know if I will be able to process the object successfully, I want to just peek() and not remove the object. I want to remove the object only if I am able to process it successfully. So, I would like a blocking peek() function. Currently, peek() just returns if the queue is empty as per the javadocs. Am I missing something? Is there another way to achieve this functionality? EDIT: Any thoughts on if I just used a thread safe queue and peeked and slept instead? ``` public void run() { while (!exit) { while (queue.size() != 0) { Object o = queue.peek(); if (o != null) { if (consume(o) == true) { queue.remove(); } else { Thread.sleep(10000); //need to backoff (60s) and try again } } } Thread.sleep(1000); //wait 1s for object on queue } } ``` Note that I only have one consumer thread and one (separate) producer thread. I guess this isn't as efficient as using a BlockingQueue... Any comments appreciated.