java - Guava 逆源奇数通用语法

Question

 /**
   * Returns a reversed view of the specified list. For example, {@code
   * Lists.reverse(Arrays.asList(1, 2, 3))} returns a list containing {@code 3,
   * 2, 1}. The returned list is backed by this list, so changes in the returned
   * list are reflected in this list, and vice-versa. The returned list supports
   * all of the optional list operations supported by this list.
   *
   * <p>The returned list is random-access if the specified list is random
   * access.
   *
   * @since Guava release 07
   */

  public static <T> List<T> reverse(List<T> list) {
    if (list instanceof ReverseList) {
      return ((ReverseList<T>) list).getForwardList();
    } else if (list instanceof RandomAccess) {
      return new RandomAccessReverseList<T>(list);
    } else {
      return new ReverseList<T>(list);
    }

我以前从未见过这种语法:

 public static <T> List<T> reverse(List<T> list)

<T> List<T> 到底是什么？意思是？我以为会是:

 public static List<T> reverse(List<T> list)

Answer 1

第一个<T>显示它是 generic method ，介绍T作为type variable 。不要忘记Lists本身不是泛型类型 - 所以如果它只是

public static List<T> reverse(List<T> list)

...您会期待什么T引用一下？

请参阅Java Generics FAQ entry for generic methods了解更多信息。