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Command line Arguments

 Command line arguments are a thing that some programs need to take into consideration. Java allows for arguments to be passed into a program easy enough. But what if you want something more complex? I've found that you have to roll your own.

So, what can we do with regular command line arguments? Well, that's an interesting question now isn't it. I suppose the simplest use of a command line argument is to check for its existence. If it exists, then we do something with that knowledge.

That's fine and dandy if you ask me, but what if we want to do something more with command line arguments? Like if the argument takes a parameter or two, what then? A while ago I found an article on the internet that shows exactly what you can do with such arguments. You would call your program, and pass it a switch like this:


java test.jar -d 47

Now -d could be whatever you want it to be. It can literally represent whatever part of your program you want it to. The 47 being passed in could be whatever you need it to be as well. So, how do we go about doing this? That's a good question.

Here's some psudo code of how we would do that.

  1. Check to see if the argument starts with a dash.
  2. If it doesn't, throw an error and alert the user.
  3. If it does contain a dash, make sure that it's at least 2 characters in length.
  4. If it's not at least 2 characters in length then the user passed in a dash and that's it, then you would throw an error.
  5. Store the dashed argument in a map of some kind, and move onto the following argument. If it doesn't begin with a dash it belongs to your first argument as a parameter for that argument.
  6. Store that value in a list within the map. You can keep building this list up for that specific argument
  7. Repeat as necessary.

I'll have to dig out the code that actually makes all of this work. But for now you get the idea.

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