Java OCA OCP Practice Question 2626

Question

Consider the following program: 

import java.util.*;

class Task implements Comparable<Task> {
        int priority;
        public Task(int val) {
                priority = val;
        }/*  w  w  w .ja va 2  s . c  o  m*/
public int compareTo(Task that) {
        if(this.priority == that.priority)
                return 0;
        else if (this.priority > that.priority)
                return -1;
        else
                return 1;
}
public String toString() {
        return new Integer(priority).toString();
}
}

class Main {
        public static void main(String []args) {
                PriorityQueue<Task> tasks = new PriorityQueue<Task>();
                tasks.add(new Task(10));
                tasks.add(new Task(15));
                tasks.add(new Task(5));
                Task task;
                while ( (task = tasks.poll()) != null) {
                        System.out.print(task + " ");
                }
        }
}

When executed, this program prints the following:

  • a) 10 10 10
  • b) 10 15 5
  • c) 5 10 15
  • d) 15 10 5
  • e) 5 5 5


d)

Note

The Task class implements Comparable<Task>, which specifies how to compare its elements.

The PriorityQueue method prioritizes the elements in the queue by calling the compareTo() method.

The compareTo() method returns -1 if the priority of the current Task object is greater than the priority of the compared Task object.

Hence the elements of the PriorityQueue are retrieved in the descending order.




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