What 's the difference between a list and a list? That is, the difference between the type parameter " " and the unbounded wildcard character ""

Source: Internet
Author: User

Difference between type parameter "<T>" and "<?>" of unbounded wildcard characters

To discuss "<T>" and "<?>", first distinguish between two different scenarios:

First, declare a generic class or generic method. Second, use a generic class or generic method. The type parameter "<T>" is primarily used for the first, declaring a generic class or generic method.
The unbounded wildcard "<?>" is primarily used for the second, using generic classes or generic methods.

In layman's parlance, "T" is what is declared when a class or method is defined, "?" Is something that is passed in at the time of the call, and the two are different concepts.

Contact Us

The content source of this page is from Internet, which doesn't represent Alibaba Cloud's opinion; products and services mentioned on that page don't have any relationship with Alibaba Cloud. If the content of the page makes you feel confusing, please write us an email, we will handle the problem within 5 days after receiving your email.

If you find any instances of plagiarism from the community, please send an email to: info-contact@alibabacloud.com and provide relevant evidence. A staff member will contact you within 5 working days.

A Free Trial That Lets You Build Big!

Start building with 50+ products and up to 12 months usage for Elastic Compute Service

  • Sales Support

    1 on 1 presale consultation

  • After-Sales Support

    24/7 Technical Support 6 Free Tickets per Quarter Faster Response

  • Alibaba Cloud offers highly flexible support services tailored to meet your exact needs.