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Java Annotations

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Using a Custom Annotation

3:20 with Chris Ramacciotti

With our @Doc annotation written, we can now use it like any other. In this video, we'll apply the annotation to the MathUtils class and a few of its methods.

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    I'm back in our workspaces project and we're ready to use our doc annotation and 0:00
    the MathUtils class. 0:04
    First, we'll need to import the annotation itself, 0:05
    import com.teamtreehouse.docgen.Doc. 0:10
    We'll start by applying the annotation to the class itself. 0:14
    And in this annotation, we'll need to include just a description since 0:18
    parameters and return types will not apply to the class. 0:21
    You can list the annotation on separate lines if you'd like to keep it well 0:25
    formatted. 0:28
    I'll say that this is a Utility class for commonly used math functions. 0:29
    Notice that I've had to explicitly list D-E-S-C. 0:38
    Remember, the only time you can omit the element name is when the element name 0:42
    is exactly value. 0:46
    Now, let's add some annotations to a few methods and make some of them incomplete 0:48
    just to verify that our tool is able to catch both successes and failures. 0:52
    For the triangle area method, I'll include a description for only one parameter. 0:58
    So include our doc annotation, I'll put this on three separate lines. 1:03
    For the description, I'll write that it calculates the area of a triangle. 1:07
    I'll abbreviate here. 1:14
    For the parameters, again, I will include a description for just one parameter. 1:16
    And again, our params element is a string array, so 1:21
    I'll have to use array notation with the curly braces. 1:24
    And for the returnVal, I will say returns the calculated area of the triangle. 1:35
    Cool. 1:44
    For the distance method, I'll make the returnVal an empty string. 1:46
    I'll include as its description that it calculates 1:57
    the distance between the given points. 2:01
    I'll include descriptions for both parameters, 2:07
    the first one being the coordinates of one point, 2:11
    the second one being the coordinates of another point. 2:15
    And finally, the returnVal, as I said, I will leave as an empty string. 2:24
    As for the quadraticRoots method, I'll leave this one out completely and 2:29
    go right to the epsilon method. 2:33
    For this one, I'll include only a description since it has no parameters and 2:36
    is a void method. 2:40
    I'll say that this displays the value of epsilon. 2:46
    The arePointsClose method won't need documentation 2:55
    to pass our tools test since it's a private method. 2:58
    And there you have it, 3:02
    a class that utilizes the annotation that we wrote ourselves. 3:03
    The writing of the doc annotation was fairly brief. 3:07
    The lengthier work for us will come in the form of examining the presence of our 3:09
    annotation on classes and methods through a technique called reflection. 3:13
    More on that next. 3:18

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