Is there a PriorityQueue implementation with fixed capacity and custom comparator?

Question

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Answer 1

Below is the implementation I used before. Complies with Peter's suggestion.

 public @interface NonThreadSafe {
 }

/**
 * A priority queue implementation with a fixed size based on a {@link TreeMap}.
 * The number of elements in the queue will be at most {@code maxSize}.
 * Once the number of elements in the queue reaches {@code maxSize}, trying to add a new element
 * will remove the greatest element in the queue if the new element is less than or equal to
 * the current greatest element. The queue will not be modified otherwise.
 */
@NonThreadSafe
public static class FixedSizePriorityQueue {
    private final TreeSet treeSet; /* backing data structure */
    private final Comparator comparator;
    private final int maxSize;

    /**
     * Constructs a {@link FixedSizePriorityQueue} with the specified {@code maxSize}
     * and {@code comparator}.
     *
     * @param maxSize    - The maximum size the queue can reach, must be a positive integer.
     * @param comparator - The comparator to be used to compare the elements in the queue, must be non-null.
     */
    public FixedSizePriorityQueue(final int maxSize, final Comparator comparator) {
        super();
        if (maxSize <= 0) {
            throw new IllegalArgumentException("maxSize = " + maxSize + "; expected a positive integer.");
        }
        if (comparator == null) {
            throw new NullPointerException("Comparator is null.");
        }
        this.treeSet = new TreeSet(comparator);
        this.comparator = treeSet.comparator();
        this.maxSize = maxSize;
    }

    /**
     * Adds an element to the queue. If the queue contains {@code maxSize} elements, {@code e} will
     * be compared to the greatest element in the queue using {@code comparator}.
     * If {@code e} is less than or equal to the greatest element, that element will be removed and
     * {@code e} will be added instead. Otherwise, the queue will not be modified
     * and {@code e} will not be added.
     *
     * @param e - Element to be added, must be non-null.
     */
    public void add(final E e) {
        if (e == null) {
            throw new NullPointerException("e is null.");
        }
        if (maxSize <= treeSet.size()) {
            final E firstElm = treeSet.first();
            if (comparator.compare(e, firstElm) < 1) {
                return;
            } else {
                treeSet.pollFirst();
            }
        }
        treeSet.add(e);
    }

    /**
     * @return Returns a sorted view of the queue as a {@link Collections#unmodifiableList(java.util.List)}
     *         unmodifiableList.
     */
    public List asList() {
        return Collections.unmodifiableList(new ArrayList(treeSet));
    }
}

I would appreciate any feedback btw.

EDIT: It seems like using a TreeSet is not very efficient after all because the calls to first() seem to take sublinear time. I changed the TreeSet to a PriorityQueue. The modified add() method looks like this:

   /**
     * Adds an element to the queue. If the queue contains {@code maxSize} elements, {@code e} will
     * be compared to the lowest element in the queue using {@code comparator}.
     * If {@code e} is greater than or equal to the lowest element, that element will be removed and
     * {@code e} will be added instead. Otherwise, the queue will not be modified
     * and {@code e} will not be added.
     *
     * @param e - Element to be added, must be non-null.
     */
    public void add(final E e) {
        if (e == null) {
            throw new NullPointerException("e is null.");
        }
        if (maxSize <= priorityQueue.size()) {
            final E firstElm = priorityQueue.peek();
            if (comparator.compare(e, firstElm) < 1) {
                return;
            } else {
                priorityQueue.poll();
            }
        }
        priorityQueue.add(e);
    }