The @Deprecated Annotation

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