Java PriorityQueue poll() Method

The poll() method of PriorityQueue class retrieves the head of this queue, and also removes it. The method returns null if this queue is empty.

Syntax

Parameter

Return Value

The poll() method returns this queue's head, and if this queue is empty returns null.

Example 1

import java.util.PriorityQueue;

public class PriorityQueuePollExample1 {
	public static void main(String[] args) {
PriorityQueue<String>Pqueue = new PriorityQueue<String>();
Pqueue.add("Ramesh");
Pqueue.add("Yasir");
Pqueue.add("Mark");
Pqueue.add("Robert");

        String val = Pqueue.poll();

System.out.println("Head of queue is: "+val);
System.out.println("Queue after using poll() method : ");
for(String xyz : Pqueue)
        {
	System.out.println(xyz);
        }   
    }
}

Test it Now

Output:

Head of queue is: Mark
Queue after using poll() method : 
Ramesh
Robert
Yasir

Example 2

import java.util.Comparator;
import java.util.PriorityQueue;
import java.util.Queue;

class Student {
int marks;
    String name;
public Student(int marks, String name) {
this.marks= marks;
this.name = name;
    }
public String toString(){
return this.name+" got "+ this.marks+" marks.";
    }
}
class sort implements Comparator<Student>{

@Override
public int compare(Student s1, Student s2) {
if(s1.marks<s2.marks)
return 1;
else if(s1.marks>s2.marks)
return -1;
return 0;
    }
}
public class PriorityQueuePollExample2 {
public static void main(String[] args) {
        Student student1 = new Student(77,"Hinna");
        Student student2 = new Student(87,"Vinni");
        Student student3 = new Student(97,"Rima");
        Queue<Student> queue = new PriorityQueue<Student>(1,new sort());
queue.add(student1);
queue.add(student2);
queue.add(student3);
System.out.println(queue.poll().name+" stood First in the class");
System.out.println(queue.poll().name+" stood Second in the class");
System.out.println(queue.poll().name+" stood Third in the class");
    }
}

Test it Now

Output:

Rima stood First in the class
Vinni stood Second in the class
Hinna stood Third in the class

Example 3

import java.util.PriorityQueue;

class Patient implements Comparable{
    String name;

public Patient(String name) {
this.name = name;
    }
@Override
public int compareTo(Object o) {
return 0;
    }
}
public class PriorityQueuePollExample3 {
public static void main(String[] args) {
PriorityQueue<Patient>Pqueue = new PriorityQueue<Patient>();
        Patient p1 = new Patient("Arnavi");
        Patient p2 = new Patient("Himani");
        Patient p3 = new Patient("Sarita");
Pqueue.add(p1);
Pqueue.add(p2);
Pqueue.add(p3);
System.out.println(Pqueue.poll().name+" can visit the doctor at first. ");
System.out.println(Pqueue.poll().name+" can visit the doctor after the first patient. ");
System.out.println(Pqueue.poll().name+" can visit the doctor after the second patient. ");
    }
}

Test it Now

Output:

Arnavi can visit the doctor at first. 
Sarita can visit the doctor after the first patient. 
Himani can visit the doctor after the second patient.

Next TopicJava PriorityQueue

← prev next →

Help Others, Please Share

Javatpoint Services

JavaTpoint offers too many high quality services. Mail us on [email protected], to get more information about given services.

Website Designing
Website Development
Java Development
PHP Development
WordPress
Graphic Designing
Logo
Digital Marketing
On Page and Off Page SEO
PPC
Content Development
Corporate Training
Classroom and Online Training
Data Entry

Training For College Campus

JavaTpoint offers college campus training on Core Java, Advance Java, .Net, Android, Hadoop, PHP, Web Technology and Python. Please mail your requirement at [email protected].
Duration: 1 week to 2 week

^{Like/Subscribe us for latest updates or newsletter}

Java PriorityQueue Class

Java PriorityQueue poll() Method

Syntax

Parameter

Return Value

Example 1

Example 2

Example 3

Help Others, Please Share

Javatpoint Services

Training For College Campus