PriorityBlockingQueue is a class provided by Java's concurrency utilities that implements the BlockingQueue interface and is used to hold a collection of elements sorted according to their natural order or by a specified Comparator. It is similar to a regular PriorityQueue, but with the added functionality of blocking on both put() and take() operations.

Here's an example of how to use PriorityBlockingQueue in Java:

1. Creating a PriorityBlockingQueue with a capacity of 10 elements and a custom Comparator:

PriorityBlockingQueue<Integer> queue = new PriorityBlockingQueue<>(10, new MyComparator());

2. Adding elements to the queue:

queue.put(1);
queue.put(2);

3. Accessing elements from the queue:

Integer element = queue.take();

4. Iterating over the elements in the queue:

for (Integer element : queue) {
    System.out.println("Element: " + element);
}

5. Removing elements from the queue:

queue.remove(1);

6. Using the peek() method to get the next element in the queue without removing it:

Integer nextElement = queue.peek();

7. Using the poll() method to get the next element in the queue and remove it:

Integer nextElement = queue.poll();

In this example, the custom Comparator is used to sort the elements in the queue in reverse order. If you don't specify a Comparator, the elements will be sorted according to their natural order.

PriorityBlockingQueue is useful in situations where you want to implement a blocking queue with a priority-based ordering of elements, for example, in a job queue where tasks need to be executed in a certain order. The blocking behavior of the put() and take() methods ensures that threads are synchronized and waiting for each other, which can help to prevent contention and reduce the chances of deadlock.