Create a PriorityQueue to Manage To-Do list

Problem Statement: Write a Java program to create a PriorityQueue to manage a to-do list with tasks having different priorities.

Here’s a Java program that demonstrates how to create a PriorityQueue to manage a to-do list with tasks having different priorities.

package com.javacodepoint.collection;

import java.util.PriorityQueue;

class Task implements Comparable<Task> {
	private String name;
	private int priority;

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

	public String getName() {
		return name;
	}

	public int getPriority() {
		return priority;
	}

	@Override
	public int compareTo(Task other) {
		// Tasks are compared based on their priorities
		return Integer.compare(this.priority, other.priority);
	}

	@Override
	public String toString() {
		return "[" + name + ", Priority: " + priority + "]";
	}
}

public class PriorityQueueToDoList {

	public static void main(String[] args) {
		PriorityQueue<Task> toDoQueue = new PriorityQueue<>();

		// Adding tasks to the to-do list with different priorities
		toDoQueue.offer(new Task("Task 1", 3));
		toDoQueue.offer(new Task("Task 2", 1));
		toDoQueue.offer(new Task("Task 3", 2));
		toDoQueue.offer(new Task("Task 4", 4));
		toDoQueue.offer(new Task("Task 5", 2));

		// Processing tasks in priority order
		while (!toDoQueue.isEmpty()) {
			Task task = toDoQueue.poll();
			System.out.println("Task Completed: " + task);
		}
	}
}

OUTPUT:

Task Completed: [Task 2, Priority: 1]
Task Completed: [Task 5, Priority: 2]
Task Completed: [Task 3, Priority: 2]
Task Completed: [Task 1, Priority: 3]
Task Completed: [Task 4, Priority: 4]

Explanation:

1. Task class: This class represents a task with a name and a priority. It implements the Comparable interface to allow tasks to be compared based on their priorities.
   • The compareTo method is implemented to compare tasks based on their priorities.
   • The toString method is overridden to provide a readable representation of a task.
2. ToDoList class: This is the main class that manages the to-do list using a PriorityQueue of tasks.
   • In the main method, we create a PriorityQueue named toDoQueue to store tasks. The tasks will automatically be ordered based on their priorities due to the priority queue.
   • We add tasks to the to-do list using the offer method, which adds tasks to the queue while maintaining their order based on priority.
   • We process tasks in priority order using a while loop. We continuously poll tasks from the toDoQueue, which removes and returns the task with the highest priority. This allows us to process tasks in order of priority.

By using a PriorityQueue, the program effectively manages a to-do list with tasks having different priorities. Tasks are automatically ordered and processed based on their priorities, ensuring that higher-priority tasks are completed first.

See also: Basic Queue Implementation using LinkedList.