- Used when we have to use arranged in order of process.
- Queue interface extends collection, so it supports all methods of collection like list and set.
- It supports methos of collection and add, offer, remove, poll peek also.
- Elements are sorted and in natural order.
package QueueInterface;
import java.util.Comparator;
import java.util.List;
import java.util.PriorityQueue;
import java.util.Queue;
class StringLengthComparator implements Comparator<String> {
@Override
public int compare(String o1, String o2) {
// TODO Auto-generated method stub
return Integer.compare(o1.length(), o2.length());
}
}
public class QueueClass {
public static void main(String[] args) {
QueueClass qc = new QueueClass();
// creating queue
Queue<String> queue = new PriorityQueue<>();
queue.offer("Apple");
queue.addAll(List.of("Zebra", "Cat", "Dog", "Owl"));
System.out.println("Queue is : " + queue);
// O/P : Queue is : [Apple, Dog, Cat, Zebra, Owl]
// it is in sorted order
// Moving head in forward direction
queue.poll();
System.out.println("Queue is : " + queue);
// O/P Queue is : [Cat, Dog, Owl, Zebra]
// creating queue using comparator
qc.queueUsingComparator();
}
public void queueUsingComparator() {
Queue<String> queue = new PriorityQueue<>(new StringLengthComparator());
queue.offer("Apple");
queue.addAll(List.of("Zebra", "Cat", "Dog", "Owl"));
System.out.println("Queue using StringLengthComparator is : " + queue);
System.out.println(queue.poll());
System.out.println(queue.poll());
System.out.println(queue.poll());
System.out.println(queue.poll());
System.out.println(queue.poll());
/*
* O/P is Queue using StringLengthComparator is : [Cat, Dog, Apple, Zebra, Owl]
* Cat Owl Dog Apple Zebra
*
* here lower length is processed first and then higher length
*/
}
}
