I am coding a questionbank with netbeans as a school project. I am using a JFrame GUI to enter question data. I need some clever way to store, edit and delete data in some file. I don´t want to use any databases. I already tried solving this with txt files but it is tedious and wont work. I need some option where I can add an entire question to the file and then when I retrieve it retrieve certain parts. The data below is how I tried solving it. I then used a scanner to read the files line by line and stop everytime a "_" is read. Is there any better way to store this. Or can i store this in a 2 dimensional array in the java program itself.If so any help or solution is appreciated
Geography_What is England's capital_Berlin_Manchester_Dover_London_D_3
Maths_What is 2+3_7_9_5_6_C_1
Economics_What is demand_idk_stuff_demand_supply_C_2
Well, if you dont want databases or any external files, the only way to "store" information is to create some data structures to do so. The issue with that is they wont persist past the lifetime of the current running application.
Id advise to use some form of external file, or set up a simple sql db. Its easy and will make the project simpler
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I'm starting on a new budgeting/allowance project and I'm trying to figure out how to save the data between opening and closing the program. Arrays seem clunky and I don't know how I would save the array data to a file anyway. I've really only worked with text files before so this is new to me.
I'm assuming a database of some sort is what I need but I don't know what I should be looking for.
I know this has to be a simple issue but I honestly don't know where to start; any help is greatly appreciated.
That is entirely for you to decide, there is no one right answer here.
You can save in a text file, e.g. CSV if very simple, otherwise JSON or XML are common choices, or in a binary file, e.g. Java serialized objects, or some embedded database file might do.
It really depends on how complex the data is, how big the file can become, whether you want to be able to edit the file directly in a text editor, and how important load/save performance is to you.
Since it's a new project and you seem fairly new to this, I'd suggest JSON or XML, whichever of the two you are more familiar with. But that's just my opinion.
It's entirely your choice.
Trying to make an app in android studio that works as a fitness helper/tracker. On a daily basis and multiple times a day, the user enters data regarding their diet/exercise. Prior to doing so, the user selects which day they're currently on, making the data they input specific to the chosen date. I want to give users the ability to retrieve any available data for a specific day on demand.
I don't quite think sharedPreferences would work, so I was thinking about just saving to internal storage as a text file. The problem is that 1) with all the different files that would be created for even a single day, I feel that it would get messy and 2) I'm not sure how how to retrieve the specific file I'd need, parse it, then output the parsed data graphically if I'm only using a single constructor to make each text file.
I haven't yet delved deeply into using a SQLite DB, it seemed somewhat excessive for this, so I'm hoping someone can either help me figure out a better way to solve the problem or enlighten me as to a more efficient method.
Thanks in advance!
I have a bit of a rookie question regarding storage of map data i a java game. I'm making a 2d tile-based game, where each tile has an id (1, 2, 3, 4 and so on...). I currently store the game data in a .txt file, where each number is seperated by a tab. Therefrom i read it via scanners .nextInt.
This method works fine, but it seems to give me a problem:
Since the level file is just a normal .txt file it is easily edited by anyone. This means that the user could just change a few numbers in the file with any kind of text editor and thereby easily cheat.
How would this be avoided? Should i store the map data differently or should i use some form of encryption?
One solution to this would be to store the data in a database, such as derby. Once the game has been exported as a jar file the casual player will never even see the file, and if they do get their hands on it, probably wouldn't know what to do with it.
Here is a nice tutorial on how to set up and connect to a simple derby database.
http://www.vogella.com/tutorials/ApacheDerby/article.html
good luck.
Java has a Serializable interface that can be used to save java objects.
API docs can be found here: http://docs.oracle.com/javase/7/docs/api/java/io/Serializable.html
This doesn't make it impossible for people to cheat and change the maps just more difficult.
If you're really worried about it you could use some form of encryption or add a checksum to further prevent tampering.
I want to insert the data at some positions in the text file without actually overwriting on the existing data.I tried RandomAccessFile ....but that also overwrites it....
Is there any way to insert the data without overwriting??
-Thanks in advance
You have to read your file and rewrite it. During this operation you have to find the place where you want to put your text and write it.
It is not possible (not with Java, and not with any other programming language) to "just" insert data in the middle of the file, without having to re-write the rest of the file. The problem is not the programming language, the problem is the way files work.
I have to use a java program . I need to understand it and then modify it. The program has a source folder. It has a lot of java files. the program has a GUI interface. i have imported the program in eclipse and i can run the program. i want to learn and understand the code but since its too big i want to only read the relevant portions of the code which i need to understand to modify / add features to the program. This program requires input data . this data can be in a CSV file or a MySql database. the immediate problem i am facing with the program is that i need to use float data as input data in one of the columns. when i put data in decimal form in the CSV file . the program has no problem in accepting it and processing it. but when i create a MYSQL database table with floating datatype as one of the column . the program while importing data gives error - "unknown data type float . add this entry is xxx.props file " even after i add the float entry in xxx.props file in the proper way just as other entries are there for other data types in xxx.props file, i still get the same error . what should i do next ? which part of the code should i study to find out the problem?
When you say it "gives error" - does it throw an exception? If so, find out where that exception is thrown from, and work backwards from there.
You haven't explained what the xxx.props file is, how you created the mysql table, or what you're then doing with it, which makes it kinda hard to give any more specific help...
Without a direct question, I can't help you much. However, I can advise you on how to solve the problem.
Learn the basics before you try to make a leap to do everything at once. Try to learn these before coming everything:
Get a working knowledge of Java
Figure out how to develop a GUI that isn't binded to your logic. (Take a look at the MVC design pattern)
Break up the big program into manageable parts
Implement your logic separately from your data access (M C part of MVC)
Use Unit Testing to verify that your components work
Implement the CSV reading, and then move it to the database
This way you have seperable components that will make your job easier to deal with, and you will learn quite a bit along the way.
You've got a lot of small questions but I think your main question is "why am I getting this 'unknown data type float' error". Without looking at any code my first suggestion would be to validate how you're inserting/updating the MySQL table. Hopefully the developer extrapolated the data tier from the UI tier meaning there should only be one or two java classes to look at to verify how the data is inserted.
Overall, it sounds like you're new to Java and application design. Try to follow how the program works from point A to point B. Hopefully the code was broken out into tiers to make it easier for you; IE the GUI is in it's own package/project and the business logic is in it's own package/project, so on and so on.