Java PriorityQueue offer() Method

The offer() method of the PriorityQueue class is used to insert the specified element into this priority queue.

Syntax

Parameter

e - It is the element to be added.

Specified By

The offer() method of the PrioriryQueue class is specified by offer() method n interface Queue<E>.

Return Value

The offer() method returns true same as defined by Queue.offer(E).

Throws

The offer() method throws:

ClassCastException - if the specified element is not compared with the elements in this priority queue as per the priority queue's ordering.
NullPointerException - if the specified element has null value.

Example 1

import java.util.PriorityQueue;
public class JavaPriorityQueueOfferExample1 {
public static void main(String[] args) {        
PriorityQueue<Integer>pQueue = new PriorityQueue<Integer>();
for(int i=5; i<15; i++)
                {
pQueue.add(new Integer(i));
                }              
System.out.println("Priority Queue values are: " +pQueue );
pQueue.offer(25);
System.out.println("Priority Queue values after addition are: " +pQueue );
                    }    
}

Output:

Priority Queue values are: [5, 6, 7, 8, 9, 10, 11, 12, 13, 14]
Priority Queue values after addition are: [5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 25]

Example 2

import java.util.PriorityQueue;
public class JavaPriorityQueueOfferExample2 {
public static void main(String[] args) {
PriorityQueue<String>pQueue = new PriorityQueue<String>();
pQueue.add("Aman"); 
pQueue.add("Asif");
pQueue.add("Harshit"); 
pQueue.add("Harman");
pQueue.add("Deepak"); 
pQueue.add("Dimple");
pQueue.add("Jass"); 
pQueue.add("Dhanil");
System.out.println("Priority Queue values are: " +pQueue );
pQueue.offer(null);        
System.out.println("Priority Queue values after addition are: " +pQueue );             
                    }
}

Output:

Priority Queue values are: [Aman, Asif, Dimple, Dhanil, Deepak, Harshit, Jass, Harman]
Exception in thread "main" java.lang.NullPointerException

Example 3

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

class Attendance {
public int rollNo;
public String name;

public Attendance(String name) {
// this.rollNo = rollNo;
this.name = name;
    }

public String toString() {
return this.name;
    }

}
class sort  implements Comparator<Attendance> {
@Override
public int compare(Attendance a, Attendance b) {
if (a.name.charAt(0) >b.name.charAt(0))
return 1;
else if (a.name.charAt(0) <b.name.charAt(0))
return -1;
return 0;
    }

}

public class JavaPriorityQueueOfferExample3 {
public static void main(String[] args) {
        Attendance a1 = new Attendance("Amit");
        Attendance a2 = new Attendance("Simran");

PriorityQueue<Attendance>Pqueue = new PriorityQueue<Attendance>(15,new sort());
Pqueue.add(a1);
Pqueue.add(a2);
        Attendance a3 = new Attendance("Raj");
        Attendance a4 = new Attendance("Barun");
Pqueue.offer(a3);
Pqueue.offer(a4);

for (Attendance xyz: Pqueue) {
System.out.println(xyz);
        }
    }
}

Output: