Using the Directory and Xlint Command Line Options

To provide motivation for the next option, let's look back at our source directories. 0:00 Earlier, we noticed that upon compiling, 0:04 our class files were placed in the same directory as our source files. 0:06 Here we see Cheese.class right next to Cheese.java, and 0:10 Main.class right next to Main.java. 0:14 Now, since we're developers, chances are that we're creating software 0:17 that will be distributed and installed elsewhere. 0:20 What we'll distribute though, are the .class files not the .Java files. 0:23 We will code the .Java files and the compiler will produce the .class files. 0:28 In an effort to preserve this separation of concerns and 0:33 keep our directories tidy, let's stick the .class files elsewhere. 0:36 We can accomplish by using another command line option, the directory or 0:40 -d option with the javac command. 0:44 Now, if you've already switched to an IDE such as IntelliJ or 0:48 Eclipse, you've noticed that those IDEs automatically create a directory for 0:51 you that contains the .class files. 0:56 Likely it's named bin, short for binary. 0:58 Out, short for output. 1:02 Or build, referring to compiling, or building, our application. 1:03 Let's create one now called out, and put all of our .class files there. 1:08 So, I'll right-click on the workspace directory and choose New Folder, 1:12 and name it out, all lower case. 1:17 Great, before we compile to the out directory let's be sure to delete our 1:20 existing .class files so we can ensure new ones are created in the out directory. 1:25 Now we're ready to compile to the out directory. 1:36 To do this after javac, I'll specify the directory option using -d and 1:40 tell the compiler to use the out directory as the destination for our .class files. 1:45 Again, we won't forget to specify our class path. 1:52 If we refresh the out directory, we will see our new class files 2:01 that were just generated as a result of our compiler statement. 2:07 Let's check it out. 2:14 If we drill down all the way to the override folder. 2:14 There is Cheese.class and Main.class. 2:17 This is really nice as it keeps the directories of our source code clean. 2:21 We're not littering them with files that we'll never directly edit. 2:26 Now if we'd like to run the application, 2:30 we'll specify the class path as the out directory. 2:31 java -cp is the out directory, and 2:36 com.teamtreehouse.override.main is the class that we'd like to run, 2:40 and there's our output again. 2:46 Cool! 2:47 From now on, any time we want to compile from the console, 2:48 we'll definitely use this approach to keep our directories organized. 2:51 Let's check out one more command line option while compiling. 2:55 You can ask the compiler to give you more information than what it does by default. 2:59 When you compile using the javac command, 3:03 you're going to be told mainly about errors. 3:05 That is, things that will prevent your code from successfully compiling. 3:08 Beyond errors, you can ask the compiler to tell you about warnings, 3:12 much like we saw with the deprecated annotation. 3:15 For this, you'll need to add a command line option. 3:19 In general, you'll add what's called the -Xlint option. 3:21 Lint is an old term that meant to flag suspicious behavior in your code before 3:25 you compiled it. 3:29 That seems to make sense here too. 3:31 Let me add a statement to the Main class, 3:33 and I'm sure you'll be able to spot the problem even before compiling. 3:35 Clear my console and let me add this statement here. 3:42 Let's see what happens when we compile and run this code. 3:51 Compile the code and it looks like we have no compiler errors, so 3:58 let's run this thing. 4:02 We get our output, but then we get an error or exception. 4:07 And we see, even if we don't understand all the gibberish that's here, 4:11 we see that it's a / by zero error. 4:15 And you already knew that was going to happen. 4:18 Let's add the excellent option to compilation to display all earnings and 4:22 see what happens. 4:27 In order to do that, while compiling we'll use the -Xlint option, 4:29 don't forget to capitalize that X. 4:34 Specify the out directory as the location for our .class files. 4:38 Don't forget our class path and the full path to 4:44 Main.java. 4:47 A warning, it's a warning for a / by zero error. 4:54 Hey, remember earlier when I said that any opportunity we get to catch an error while 4:58 compiling, as opposed to while our app is running, is an opportunity we'll take. 5:01 Yep, here it is again. 5:06 And that's what the -Xlint option can do for you. 5:08