public LinkQueue() { front = rear = null; size = 0; }
public QueueNode() { data = default(T); next = null; }
public QueueNode(T val) { data = val; next = null; }
public QueueNode(QueueNode <T> p) { next = p; }
public void Clear() { front = rear = null; size = 0; }
public QueueNode(T val, QueueNode <T> p) { data = val; next = p; }