Okay so i am working on a game based on a Trading card game in java. I Scraped all of the game peices’ “information” into a csv file where each row is a game peice and each column is a type of attribute for that peice. I have spent hours upon hours writing code with Buffered reader and etc. trying to extract the information from my csv file into a 2d Array but to no avail. My csv file is linked Here: http://dl.dropbox.com/u/3625527/MonstersFinal.csv I have one year of computer science under my belt but I still cannot figure out how to do this.
So my main question is how do i place this into a 2D array that way i can keep the rows and columns?
Well, as mentioned before, some of your strings contain commas, so initially you’re starting from a bad place, but I do have a solution and it’s this:
——— If possible, rescrape the site, but perform a simple encoding operation when you do. You’ll want to do something like what you’ll notice tends to be done in autogenerated XML files which contain HTML; reserve a ‘control character’ (a printable character works best, here, for reasons of debugging and… well… sanity) that, once encoded, is never meant to be read directly as an instance of itself. Ampersand is what I like to use because it’s uncommon enough but still printable, but really what character you want to use is up to you. What I would do is write the program so that, at every instance of “,”, that comma would be replaced by “&c” before being written to the CSV, and at every instance of an actual ampersand on the site, that “&” would be replaced by “&a”. That way, you would never have the issue of accidentally separating a single value into two in the CSV, and you could simply decode each value after you’ve separated them by the method I’m about to outline in…
——– Assuming you know how many columns will be in each row, you can use the StringTokenizer class (look it up- it’s awesome and built into Java. A good place to look for information is, as always, the Java Tutorials) to automatically give you the values you need in the form of an array.
It works by your passing in a string and a delimiter (in this case, the delimiter would be ‘,’), and it spitting out all the substrings which were separated by those commas. If you know how many pieces there are in total from the get-go, you can instantiate a 2D array at the beginning and just plug in each row the StringTokenizer gives them to you. If you don’t, it’s still okay, because you can use an ArrayList. An ArrayList is nice because it’s a higher-level abstraction of an array that automatically asks for more memory such that you can continue adding to it and know that retrieval time will always be constant. However, if you plan on dynamically adding pieces, and doing that more often than retrieving them, you might want to use a LinkedList instead, because it has a linear retrieval time, but a much better relation than an ArrayList for add-remove time. Or, if you’re awesome, you could use a SkipList instead. I don’t know if they’re implemented by default in Java, but they’re awesome. Fair warning, though; the cost of speed on retrieval, removal, and placement comes with increased overhead in terms of memory. Skip lists maintain a lot of pointers.
If you know there should be the same number of values in each row, and you want them to be positionally organized, but for whatever reason your scraper doesn’t handle the lack of a value for a row, and just doesn’t put that value, you’ve some bad news… it would be easier to rewrite the part of the scraper code that deals with the lack of values than it would be to write a method that interprets varying length arrays and instantiates a Piece object for each array. My suggestion for this would again be to use the control character and fill empty columns with &n (for ‘null’) to be interpreted later, but then specifics are of course what will individuate your code and coding style so it’s not for me to say.
edit: I think the main thing you should focus on is learning the different standard library datatypes available in Java, and maybe learn to implement some of them yourself for practice. I remember implementing a binary search tree- not an AVL tree, but alright. It’s fun enough, good coding practice, and, more importantly, necessary if you want to be able to do things quickly and efficiently. I don’t know exactly how Java implements arrays, because the definition is “a contiguous section of memory”, yet you can allocate memory for them in Java at runtime using variables… but regardless of the specific Java implementation, arrays often aren’t the best solution. Also, knowing regular expressions makes everything much easier. For practice, I’d recommend working them into your Java programs, or, if you don’t want to have to compile and jar things every time, your bash scripts (if your using *nix) and/or batch scripts (if you’re using Windows).