Java Collection : Queue

Queue extends Collection interface.Elements in Queue are in the processing order.Queue have a queue policy for yielding the next element in the Queue.Head position of the queue provides the next element for processing.

Queue<String> q = new PriorityQueue<String>();

              q.add("Test");

              System.out.println(q);

              q.offer("Test1");

       System.out.println(q);

add() throws IllegalStateException if queue is full.

q.poll();

              System.out.println(q);

              q.remove();

              System.out.println(q);

  poll() and remove() methods remove the element from the queue.If Queue is empty remove() throws NoSuchElementException.

       q.add("Test");

       System.out.println(q.peek());

System.out.println(q.element());

peek() and element() methods wont delete the elements.

Following constructors for Priority Queues are supported .
PriorityQueue(int initialCapacity)
PriorityQueue(int initialCapacity, Comparator<? super E > c)
PriorityQueue(PriorityQueue<? extends E> pq)
PriorityQueue(SortedSet < ? extends E> set)

package collections;

import java.util.ArrayList;
import java.util.PriorityQueue;
import java.util.Queue;

public class QueueTest {
    /**
     * @param args
     */
    /**
     * @param args
     */
    public static void main(String[] args) {

        // Add operations
        Queue<String> q = new PriorityQueue<String>();
        q.add("Test");
        System.out.println(q);

        q.offer("Test1");
        System.out.println(q);

        q.poll();
        System.out.println(q);

        q.remove();
        System.out.println(q);

        q.add("Test");
        System.out.println(q.peek());
        System.out.println(q.element());

        ArrayList<String> a = new ArrayList<String>();
        a.add("t1");
        a.add("t2");
        a.add("t3");

        PriorityQueue<String> pq = new PriorityQueue<String>(a);
        System.out.println(pq);

    }
}