PriorityQueue in Java

A PriorityQueue in Java is a type of queue that stores elements in a way such that the element with the highest priority is always at the front of the queue. It is implemented as a binary heap, providing an efficient way to access and manage elements based on priority.

Key Properties of PriorityQueue

Elements are ordered based on their natural ordering based on the specified Comparator provided at queue construction time.

The PriorityQueue is not synchronized, hence if you are looking for the thread-safety option, you can usePriorityBlockingQueue.

The queue has no fixed size, it can grow as elements are added.

Use PriorityQueue when you need to manage tasks or elements that should be processed in a priority order.

Example: Suppose you are developing a task management system where tasks have different priorities. Higher-priority tasks should be processed before lower-priority tasks.

class 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 String toString() {  
        return "Task{name='" + name + "', priority=" + priority + "}";  
    }  
}  

public class TaskManager {  
    public static void main(String[] args) {  
        PriorityQueue<Task> taskQueue = new PriorityQueue<>(Comparator.comparingInt(Task::getPriority).reversed());  
        taskQueue.add(new Task("Task 1", 3));  
        taskQueue.add(new Task("Task 2", 1));  
        taskQueue.add(new Task("Task 3", 4));  
        taskQueue.add(new Task("Task 4", 2));  

        System.out.println("Printing tasks based on priority:");  
        while (!taskQueue.isEmpty()) {  
            Task task = taskQueue.poll();  
            System.out.println("Processing " + task);  
        }  
    }  
}

Output:

Printing tasks based on priority:
Processing Task{name='Task 3', priority=4}
Processing Task{name='Task 1', priority=3}
Processing Task{name='Task 4', priority=2}
Processing Task{name='Task 2', priority=1}