LinkedQueue.java

public class SampleLinkedQueue<E> {
    static class Node<E> {
        Node next;
        E value;
    }

    Node<E> head;
    Node<E> tail;
    SampleLinkedQueue(){
        head = tail = new Node<E>();
    }
    void offer(E e) {
        head = head.next = new Node<E>();
        head.value = e;
    }
    E poll() {
        if (tail.next == null) return null;

        tail = tail.next;
        E e = tail.value;
        tail.value = null;
        return e;
    }
}