java unbound wildcard <?> vs <T>

Question

I am confusing that if the following method are same? Are there any subtle differences?

Your advice are very appreciated.

method 1

public static double sumOfList(List<?> list) {}

method 2

public static <T> double sumOfList(List<T> list) {}

Answer 1

在方法内部,您可以T 在第二种情况下使用.

你不能在第一种情况下.

考虑这个例子

private static <T> void printList(List<T> list) {
for (T t: list) {
    System.out.println(t);
}

}