问为什么输出与预期的不同？

EN

import java.util.*;
class TestCollection12 {
    public static void main(String args[]) {

        PriorityQueue<String> queue = new PriorityQueue<String>();
        queue.add("Amit");
        queue.add("Vijay");
        queue.add("Karan");
        queue.add("Jai");
        queue.add("Rahul");

        System.out.println("head:"+queue.element());
        System.out.println("head:"+queue.peek());

        System.out.println("iterating the queue elements:");
        Iterator itr=queue.iterator();
        while (itr.hasNext()) {
            System.out.println(itr.next());
        }

        queue.remove();
        queue.poll();

        System.out.println("after removing two elements:");
        Iterator<String> itr2=queue.iterator();
        while (itr2.hasNext()) {
            System.out.println(itr2.next());
        }
    }
}

amit amit amit vijay karan jai rahul
karan jai rahul