a_169_PriorityQueue.java

import java.util.PriorityQueue ;

public class a_169_PriorityQueue {

    // PQ for Objects
    static class Student implements Comparable<Student> {   // overriding 
        String name ;
        int rank ;

        public Student(String name, int rank){
            this.name = name ;
            this.rank = rank ;
        }

        @Override
        public int compareTo(Student s2){
            return this.rank - s2.rank  ;
        }

    }

    public static void main(String[] args) {

        PriorityQueue<Student> pq = new PriorityQueue<>() ;
        // reverse priority 
    // PriorityQueue<Student> pq = new PriorityQueue<>(Comparator.reverseOrder()) ;

        pq.add(new Student("A", 4)) ;  // O(logn)
        pq.add(new Student("B", 5)) ;
        pq.add(new Student("C", 2)) ;
        pq.add(new Student("D", 12)) ;

        while(!pq.isEmpty()){
            System.out.println(pq.peek().name +"->"+ pq.peek().rank);   // O(1)
            pq.remove() ;      // O(logn)
        }
        
        
    }
}