How can I implement a custom priority queue in Java?

How can I implement a custom priority queue in Java?

You can create a custom priority queue in Java by implementing the PriorityQueue class and defining your own comparator.

Can you show me a simple example of that?

Sure! Here's a basic example:

import java.util.*;

class CustomObject {
    int priority;
    String name;

    CustomObject(int priority, String name) {
        this.priority = priority;
        this.name = name;
    }
}

class CustomComparator implements Comparator<CustomObject> {
    public int compare(CustomObject o1, CustomObject o2) {
        return Integer.compare(o1.priority, o2.priority);
    }
}

public class Main {
    public static void main(String[] args) {
        PriorityQueue<CustomObject> queue = new PriorityQueue<>(new CustomComparator());
        queue.add(new CustomObject(2, "Task 2"));
        queue.add(new CustomObject(1, "Task 1"));
        queue.add(new CustomObject(3, "Task 3"));

        while (!queue.isEmpty()) {
            System.out.println(queue.poll().name);
        }
    }
}

This will print the tasks in order of their priority.

What if I want to change the priority of an existing element?

You would need to remove the element, change its priority, and then reinsert it into the queue. Unfortunately, PriorityQueue does not support priority updates directly.