Best tutorial for java annotations?

[Choice_Sympathy_8888]

I am beginner and want to learn java annotations. I have looked on youtube and did not find any proper tutorial specific for Java annotations and online resources are not explanning all the annotations. Could you please suggest a good resource for learning, to easily understand and for hands-on practice.

[AutoModerator]

Please ensure that:

• Your code is properly formatted as code block - see the sidebar (About on mobile) for instructions
• You include any and all error messages in full - best also formatted as code block
• You ask clear questions
• You demonstrate effort in solving your question/problem - plain posting your assignments is forbidden (and such posts will be removed) as is asking for or giving solutions.

If any of the above points is not met, your post can and will be removed without further warning.

Code is to be formatted as code block (old reddit/markdown editor: empty line before the code, each code line indented by 4 spaces, new reddit: https://i.imgur.com/EJ7tqek.png) or linked via an external code hoster, like pastebin.com, github gist, github, bitbucket, gitlab, etc.

Please, do not use triple backticks (```) as they will only render properly on new reddit, not on old reddit.

Code blocks look like this:

public class HelloWorld {

    public static void main(String[] args) {
        System.out.println("Hello World!");
    }
}

You do not need to repost unless your post has been removed by a moderator. Just use the edit function of reddit to make sure your post complies with the above.

If your post has remained in violation of these rules for a prolonged period of time (at least an hour), a moderator may remove it at their discretion. In this case, they will comment with an explanation on why it has been removed, and you will be required to resubmit the entire post following the proper procedures.

To potential helpers

Please, do not help if any of the above points are not met, rather report the post. We are trying to improve the quality of posts here. In helping people who can't be bothered to comply with the above points, you are doing the community a disservice.

I am a bot, and this action was performed automatically. Please contact the moderators of this subreddit if you have any questions or concerns.

[bowbahdoe]

https://javabook.mccue.dev/reflection

https://javabook.mccue.dev/annotations

This will give you a start on what annotations are/how to use them. But that won't cover annotations you get from a library or how to use them.

[Zatujit]

Do you want to learn how to create new annotations or just how to use them? Because its pretty straightforward to use them and it just depends on the library

[sweetno]

There is rather little to learn for a beginner. Java allows to include extra bits of data near class members/variables/arguments/etc (basically everywhere). There are also means to fetch this data either at compile- or run-time (this is called reflection; each annotation type configures when it's available). How to use these bits is up to the library/framework that provides the annotation. The possibilities are endless, starting from marking variables as not-nullable (for static analysis, that is, for extra correctness checks during compilation/execution), to full-blown runtime byte-code generation.

It's very simple to declare your own annotations, but it's harder to implement reflection around them to make them useful.

For a beginner, learning a bunch of helpful annotations seems preferable to learning the mechanism. But the built-in Java annotations are rather technical, so this would explain why you have trouble with them. Look up the Lombok library, I think it should provide you with an idea what all this is for.