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The @Deprecated Annotation

3:31 with Chris Ramacciotti

The `@Deprecated` annotation allows us to mark methods, classes, and fields for future deletion, giving other developers a compiler message to update their code. In this video we'll see how the `@Deprecated` annotation provides a way for us to be responsible and courteous developers.

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    Onto our next built-in annotation, deprecated. 0:00
    This annotation is placed on methods or classes that are still functional but 0:04
    will be phased out in a future release. 0:07
    So, developers should update their code base as soon as is reasonable. 0:09
    If at all possible, 0:14
    we don't want to break existing code that is using a method we want to deprecate. 0:15
    Let's take a look at an example to illustrate how using the deprecated 0:20
    annotation can make us courteous developers. 0:24
    In the deprecated package of the same workspace's project, 0:28
    consider the Seller class. 0:31
    It has a single method in there called, placeAdInNewspaper(). 0:34
    Upon updating our class for the next release, we decide we wanna 0:38
    phase out this method and provide a new method called postInCraigslist(). 0:42
    Adding the new method is pretty straightforward. 0:47
    Let's create that now. 0:49
    I'll make this one public void as well, postInCraigslist(). 0:51
    I'll add a couple parameters, just for demonstration purposes. 0:58
    We'll get the text for the ad in there, 1:02
    as well as a list of images that we might want to include with our Craigslist post. 1:04
    And then here, we'll do all of the new school stuff. 1:11
    Since I've newly introduced the list and image classes to this file, 1:18
    I'll add those import statements now. 1:22
    For the list, that's java.util.list. 1:26
    And for image, that's java.awt.image. 1:29
    You might think that if we are going to get rid of the old method anyway, 1:37
    we should just delete it now. 1:40
    But, if we do that, then another developer who is using our updated library, 1:43
    might find herself scrambling because her code no longer compiles. 1:48
    I can demonstrate that now. 1:52
    Down in my console, I'll switch to the source directory. 1:53
    And I will compile with the javac command. 1:56
    And when I do that, 2:05
    you can see that an error has indeed occurred in the main class. 2:06
    And this is because right here, I have called the method placeAdInNewspaper(). 2:11
    A better solution, would be to communicate to 2:18
    other developers that the newspaper method is going to be phased out. 2:21
    To do this, we can add the deprecated annotation to it. 2:25
    This will force the compiler to generate a warning. 2:29
    The nice thing about this being a warning, is that it won't prevent our code from 2:32
    compiling, but it will give us an informative message. 2:36
    [SOUND] Another cool thing is that most IDEs will give you a visual indication of 2:39
    this wherever you try to call a deprecated method, 2:44
    usually by crossing out the method call. 2:46
    This is a good heads up to other developers that their code should be 2:49
    updated, because a future release will no longer have this method. 2:52
    Kind of like your highschool teacher, crossing out a phrase on your research 2:56
    paper, indicating that you need to use alternative wording. 2:59
    Instead of deleting the message, which I will undo now, 3:04
    let's add the deprecated annotation to it. 3:09
    And now, when we recompile, we get a nice heads up from the compiler. 3:14
    Indeed, this is much nicer than a broken application that does not compile. 3:21
    It gives developers a chance to update their code to use the preferred methods. 3:26

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