Related
In my program, a user can pass 4 possible dates. 3/31, 6/30, 9/30 and 12/31.
However, the user may request data for any year. For example, they can ask for 6/30/15, or 6/30/88, or 6/30/16.
However, there are only two possible flows which my program can take. The rule is simple enough, and it is as follows:
If the requested date begins with a 3/31 or 9/30, then take flow #1.
If the requested date begins with a 6/30 or 12/31, then take flow #2.
I could have hardcoded this but since there are years involved, we cannot do this. Also, I know that we can't use regular expressions with switch statements.
My Code:
I wrote the following code in which I am first converting the variable reportDate into a String. Then, I use an if statement to determine whether the passed date was either "6/30/*" or "12/31. If so, I will add a method in the if condition to do something with that date. In the else portion, I will assume that the passed date must be "3/31/" or "9/30/"
String requestedDate = Util.dateTimeToShortString(reportDate);
if (requestedDate.matches("6/30/.*") | requestedDate.matches("12/31/.*")) {
String twoQuartersBackDate = requestedDate;
}
String oneQuarterBackDate = requestedDate;
I'm not very comfortable with how this code is assuming flow #1, based on whether it finds a match on the if condition. There must be a better way to do this. Ideally, I would like to make it so that it would only accept dates from the 4 scenarios (quarters) I mentioned. Can anyone help me make this code more robust? I feel like it's amateurish at this point. Thank you.
Two tips that I picked up:
The || operator would be more suited (efficient) in this case as we only need to determine if the first condition is true.
Since regular expressions can be slower to compute, using "startsWith" would be an ideal approach.
example:
if (requestedDate.startsWith("6/30/") | requestedDate.startsWith("12/31/")) {
I am trying to write a java program (which is part of an assignment) which allows users to input their own function, and then the program calculates it and gets a value.
I have actually written a program that calculates an IVP (Initial Value Problem) using the Euler-Cauchy method. My initial function was -2*t*u^2.
However, what if I want to work on 4*t*u^3 instead or some other formula?
I tried getting the formula as String from the user, but I am having difficulty in matching a particular variable (e.g. t or u) to a number.
Use the String.replace() function to convert the u and t from the formula string to the actual variables, then take a good look at this Stack Overflow question: Convert String to Code
I am using freemarker and trying to display numbers in this format: $3,343,434.00 for example. This was easily taken care of by using ${total?string.currency} (assuming "total" is some number).
However, when I have negative numbers, it's showing them like this: ($343.34) instead of this: -$343.34. I need the negative sign instead of the parenthesis. Is there a way I could customize the formatting so it does everything that the string.currency did but replace the negative value behavior? I am relatively new to freemarker, so detailed responses are appreciated!
You can also try ?string(",##0.00"). However in this case you need to explicitly add $ and - sign would be after $ in case of negative numbers.
<#local total = 3343434/>
$ ${total?string(",##0.00")} //$ 3,343,434.00
<#local total = -3343434/>
$ ${total?string(",##0.00")} //$ -3,343,434.00
OR in case if you want what was expected you can replace the strings.
<#local total = -3343434/>
<#local total = "$ " + total?string(",##0.00")/>
${total?replace('$ -','- $')} //- $3,343,434.00
Update: Since FreeMarker 2.3.24 you can define named custom number formats, which can be an alias to a number format pattern (or even a formatter implemented in Java, but that level of flexibility isn't needed in this case). So add a custom number format called "money" as an alias to "ยค,##0.00" to the FreeMarker configuration, and then you can write something like ${total?string.#money}. See: http://freemarker.org/docs/pgui_config_custom_formats.html
Currently FreeMarker just uses the formatting facility of the Java platform, so it's only as configurable as that (assuming you want to use ?string and ?string.somethingPredefiendHere). Which is not much... but, in general, the formatting categories provided by the Java platform is not fine-gradient enough anyway, I mean, you don't have application-domain categories like, price-of-product, a salary, a price on the stock, etc. (This demand is more frequent with non-currency numbers though.) So I think, generally, you want to make a formatter function, that you can use like ${salary(someNumber)}, ${price(someNumber)}, etc. Those functions can be implemented in a commonly #included/#imported template like a #function or in Java by using #assign salary = 'com.example.SalarayMethod'?new() in place of #function, where com.example.SalarayMethod is a TemplateMethodModelEx.
How about taking a mod of your number, convert it to the required string format and finally add a '-' prefix to the final string. You can retain the default format in just two steps.
Freemarker uses the currency formatting provided by the Java platform.
It requires a little tweaking of the DecimalFormat returned by NumberFormat.getCurrencyInstance() (which is what is called when you call .currency). You can see examples of it here.
However, that said it will likely be more effective for you to create a macro in freemarker to call which will handle your specific formatting.
Sorry for not having an example of what that macro would look like, but it's a good starter into macros in freemarker since you are just learning.
You might investigate if you can supply a custom format using the exposed configuration for number formats that will meet your needs.
If you want to maintain the default currency formatting (in case you need to use a locale other than '$'), you can just replace the parentheses like so:
${transaction.amount?string.currency?replace("(","-")?replace(")","")}
This will work without error regardless of if a number is negative or positive.
TIP: Make sure the number is actually a number with the ?number directive before converting to a currency format
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).
I think the way you've scraped the data makes this problem more difficult than it needs to be. Your scrape seems inconsistent and difficult to work with given that most values are surrounded by quotes inconsistently, some data already has commas in it, and not each card is on its own line.
Try re-scraping the data in a much more consistent format, such as:
R1C1|R1C2|R1C3|R1C4|R1C5|R1C6|R1C7|R1C8
R2C1|R2C2|R2C3|R2C4|R2C5|R2C6|R2C7|R3C8
R3C1|R3C2|R3C3|R3C4|R3C5|R3C6|R3C7|R3C8
R4C1|R4C2|R4C3|R4C4|R4C5|R4C6|R4C7|R4C8
A/D Changer|DREV-EN005|Effect Monster|Light|Warrior|100|100|You can remove from play this card in your Graveyard to select 1 monster on the field. Change its battle position.
Where each line is definitely its own card (As opposed to the example CSV you posted with new lines in odd places) and the delimiter is never used in a data field as something other than a delimiter.
Once you've gotten the input into a consistently readable state, it becomes very simple to parse through it:
BufferedReader br = new BufferedReader(new FileReader(new File("MonstersFinal.csv")));
String line = "";
ArrayList<String[]> cardList = new ArrayList<String[]>(); // Use an arraylist because we might not know how many cards we need to parse.
while((line = br.readLine()) != null) { // Read a single line from the file until there are no more lines to read
StringTokenizer st = new StringTokenizer(line, "|"); // "|" is the delimiter of our input file.
String[] card = new String[8]; // Each card has 8 fields, so we need room for the 8 tokens.
for(int i = 0; i < 8; i++) { // For each token in the line that we've read:
String value = st.nextToken(); // Read the token
card[i] = value; // Place the token into the ith "column"
}
cardList.add(card); // Add the card's info to the list of cards.
}
for(int i = 0; i < cardList.size(); i++) {
for(int x = 0; x < cardList.get(i).length; x++) {
System.out.printf("card[%d][%d]: ", i, x);
System.out.println(cardList.get(i)[x]);
}
}
Which would produce the following output for my given example input:
card[0][0]: R1C1
card[0][1]: R1C2
card[0][2]: R1C3
card[0][3]: R1C4
card[0][4]: R1C5
card[0][5]: R1C6
card[0][6]: R1C7
card[0][7]: R1C8
card[1][0]: R2C1
card[1][1]: R2C2
card[1][2]: R2C3
card[1][3]: R2C4
card[1][4]: R2C5
card[1][5]: R2C6
card[1][6]: R2C7
card[1][7]: R3C8
card[2][0]: R3C1
card[2][1]: R3C2
card[2][2]: R3C3
card[2][3]: R3C4
card[2][4]: R3C5
card[2][5]: R3C6
card[2][6]: R3C7
card[2][7]: R4C8
card[3][0]: R4C1
card[3][1]: R4C2
card[3][2]: R4C3
card[3][3]: R4C4
card[3][4]: R4C5
card[3][5]: R4C6
card[3][6]: R4C7
card[3][7]: R4C8
card[4][0]: A/D Changer
card[4][1]: DREV-EN005
card[4][2]: Effect Monster
card[4][3]: Light
card[4][4]: Warrior
card[4][5]: 100
card[4][6]: 100
card[4][7]: You can remove from play this card in your Graveyard to select 1 monster on the field. Change its battle position.
I hope re-scraping the information is an option here and I hope I haven't misunderstood anything; Good luck!
On a final note, don't forget to take advantage of OOP once you've gotten things worked out. a Card class could make working with the data even simpler.
I'm working on a similar problem for use in machine learning, so let me share what I've been able to do on the topic.
1) If you know before you start parsing the row - whether it's hard-coded into your program or whether you've got some header in your file that gives you this information (highly recommended) - how many attributes per row there will be, you can reasonably split it by comma, for example the first attribute will be RowString.substring(0, RowString.indexOf(',')), the second attribute will be the substring from the first comma to the next comma (writing a function to find the nth instance of a comma, or simply chopping off bits of the string as you go through it, should be fairly trivial), and the last attribute will be RowString.substring(RowString.lastIndexOf(','), RowString.length()). The String class's methods are your friends here.
2) If you are having trouble distinguishing between commas which are meant to separate values, and commas which are part of a string-formatted attribute, then (if the file is small enough to reformat by hand) do what Java does - represent characters with special meaning that are inside of strings with '\,' rather than just ','. That way you can search for the index of ',' and not '\,' so that you will have some way of distinguishing your characters.
3) As an alternative to 2), CSVs (in my opinion) aren't great for strings, which often include commas. There is no real common format to CSVs, so why not make them colon-separated-values, or dash-separated-values, or even triple-ampersand-separated-values? The point of separating values with commas is to make it easy to tell them apart, and if commas don't do the job there's no reason to keep them. Again, this applies only if your file is small enough to edit by hand.
4) Looking at your file for more than just the format, it becomes apparent that you can't do it by hand. Additionally, it would appear that some strings are surrounded by triple double quotes ("""string""") and some are surrounded by single double quotes ("string"). If I had to guess, I would say that anything included in a quotes is a single attribute - there are, for example, no pairs of quotes that start in one attribute and end in another. So I would say that you could:
Make a class with a method to break a string into each comma-separated fields.
Write that method such that it ignores commas preceded by an odd number of double quotes (this way, if the quote-pair hasn't been closed, it knows that it's inside a string and that the comma is not a value separator). This strategy, however, fails if the creator of your file did something like enclose some strings in double double quotes (""string""), so you may need a more comprehensive approach.
I want to represent a set of labelled instances (data) in a file to be fed in to LibSVM as training data. For the problem mentioned in this question. It will include,
Login date
Login time
Location (country code?)
Day of the week
Authenticity (0 - Non Authentic, 1 - Authentic) - The Label
How can I format this data to be input to the SVM?
Are you asking about the data format or how to convert the data? For the latter you're going to have to experiment to find the right way to do this. The general idea is to convert your data into a nominal or ordinal value attribute. Some of these are simple - #4, #6 - some of these are going to be tough - #1-#3.
For example, you could represent #1 as three attributes of day, month and year, or just one by converting it to a UNIX like timestamp.
The IP is even harder - there's no straightforward way to convert that into a meaningful ordinal value. Using every IP as a nominal attribute might not be useful depending on your problem.
Once you figure this out, convert your data, check the LibSVM docs. The general format is followed by : i.e., +1 1:0 2:0 .. etc
I believe there is an unstated assumption in the previous answers. The unstated assumption is that users of libSVM know that they should avoid putting categorical data into the classifier.
For example, libSVM will not know what to do with country codes. If you are trying to predict which visitors are most likely to buy something on your site then you could have problems if USA is between Chad and Niger in your country code list. The bulge from USA will likely skew predictions for the countries located near it.
To fix this I would create one category for each country under consideration (and perhaps an 'other' category). Then for each instance you want to classify, I would set all the country categories to zero except the one to which the instance belongs. (To do this with the libSVM sparse file format, this isn't really a big deal).