为什么需要Java中LinkedList的poll（）方法的最终def(Why need final def in poll() method of LinkedList in Java)

/**
 * Retrieves and removes the head (first element) of this list.
 *
 * @return the head of this list, or {@code null} if this list is empty
 * @since 1.5
 */
public E poll() {
    final Node<E> f = first; //why final here? <<-------- ******* --------
    return (f == null) ? null : unlinkFirst(f);
}
 
 您好，我正在阅读JDK 1.7的源代码。 在LinkedList.java的上面代码片段中，我无法理解为什么在poll（）方法中需要'final'。 为什么不 ： 
 
public E poll() {
    return (first == null) ? null : unlinkFirst(first);
}
 
 你能分享实施的见解吗？ 谢谢。 

/**
 * Retrieves and removes the head (first element) of this list.
 *
 * @return the head of this list, or {@code null} if this list is empty
 * @since 1.5
 */
public E poll() {
    final Node<E> f = first; //why final here? <<-------- ******* --------
    return (f == null) ? null : unlinkFirst(f);
}
 
Hi there, I'm reading the source code of JDK 1.7. In above code snippet in LinkedList.java, I cannot understand why need 'final' in poll() method. Why not : 
 
public E poll() {
    return (first == null) ? null : unlinkFirst(first);
}
 
Can you share the insight of the implementation? Thanks.

原文：https://stackoverflow.com/questions/27628056