Java Queue Interface

The Queue interface basically orders the element in FIFO(First In First Out)manner.

Methods of Queue Interface :

1. public boolean add(object);
2. public boolean offer(object);
3. public remove();
4. public poll();
5. public element();
6. public peek();

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PriorityQueue class:

The PriorityQueue class provides the facility of using queue. But it does not orders the elements in FIFO manner.

Example of PriorityQueue

1. import java.util.*;  
2. class TestCollection12{  
3. public static void main(String args[]){  
4.   
5. PriorityQueue<String> queue=new PriorityQueue<String>();  
6. queue.add("Amit");  
7. queue.add("Vijay");  
8. queue.add("Karan");  
9. queue.add("Jai");  
10. queue.add("Rahul");  
11.   
12. System.out.println("head:"+queue.element());  
13. System.out.println("head:"+queue.peek());  
14.   
15. System.out.println("iterating the queue elements:");  
16. Iterator itr=queue.iterator();  
17. while(itr.hasNext()){  
18. System.out.println(itr.next());  
19. }  
20.   
21. queue.remove();  
22. queue.poll();  
23.   
24. System.out.println("after removing two elements:");  
25. Iterator<String> itr2=queue.iterator();  
26. while(itr2.hasNext()){  
27. System.out.println(itr2.next());  
28. }  
29.   
30. }  
31. }  

Output:head:Amit
       head:Amit
       iterating the queue elements:
       Amit
       Jai
       Karan
       Vijay
       Rahul
       after removing two elements:
       Karan
       Rahul
       Vijay