How Can I Customize the Sort Order of a PriorityQueue?

Customizing Sort Order in a PriorityQueue

A PriorityQueue is a useful data structure that maintains a sorted order of its elements. By default, it sorts based on the natural ordering of its elements. To customize this order, you can use a Comparator.

Using a Comparator

The PriorityQueue constructor has an overload that takes a Comparator as an argument. This comparator defines the sorting criteria for the queue. For example, consider a PriorityQueue that sorts strings based on their length:

Comparator<String> comparator = new StringLengthComparator();
PriorityQueue<String> queue = new PriorityQueue<>(10, comparator);

Comparator Implementation

The StringLengthComparator class implements the Comparator interface:

public class StringLengthComparator implements Comparator<String> {
    public int compare(String x, String y) {
        return x.length() - y.length();
    }
}

By comparing string lengths, the comparator establishes the desired sort order.

Offer vs. Add

The offer and add methods both add an element to the queue. However, offer returns true if the element is successfully added, while add throws an exception if the queue is full. In the case of a PriorityQueue, which is unbounded, there is no functional difference between the two methods.

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