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.
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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
Click here to see a screenshot of the assignment
Here is how the Navigation.csv looks like, where I take data from
https://pastebin.com/JXnaRTzi <-- Click on the link for code - this is my code so far, I am reading the file and making objects from each entry
Guys I need help with this assignment. I chose to do it in Java, but really it doesn't matter. I need advise and help for making the right approach on this kind of problem so it can work on a larger file. What kind of data structures should I use and maybe if it's no bother, give me a solution. I am a new developer and I'm trying to get into backend and frankly I'm a bit lost.
Click on links above to see the task details.
How to call a Minizinc model from a Java program with arrays as passed-on parameters?
Is there any special command for doing this?
I frequently do the same but in python. There is probably not any module or extension that can integrate the call in any convenient way but it is quite easy to just call another program.
Since I have not tried it in Java, I will let another stack overflow post guide you: Execute external program in java.
You can pass the parameters either as -D "var_int_name=10;var_int_array=[1,2,3];" or you can supply a data file as the last argument in the call to MiniZinc.
A general tip is to make the output from your MiniZinc model very easy to recognise and parse since many solvers print extra stuff and not just the solution. For example does MiniZinc itself print ---------- between solution. Surround the answer with & or any other sign that is easy to find and parse by a computer. You might also want to verify that you indeed got a solution back.
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 finished first year comp sci. And i want to spend some time working on the things they have taught us in the first year (lot of java and a bit of C)...
Anyways as a project, i wanted to do something i need, and what i need is a program to run through my movie folder and get the ratings and some basic info from IMDB...
I'm not sure where to start, i think i can handle the parts about reading the folder names, getting rid of the junk from the name to get the actual name and stuff.. Also i can handle the GUI but i don't know how i can talk to IMDB... what steps should i take to complete this project. I have about a month before school starts and i want to finish it before then...Thanks for all the input
EDIT:
Also can you guys tell me what i should start with and then move on to what? As in should i start with the GUI first or have the code that reads in the folder names and filters the names... I only wrote one program as an assignment in school and it was basically outlined step by step so i just wanna know what i should start with
You've made a very good start by decomposing the problem, identifying the kind of components you need and focusing on (an important) one that you don't know how to do.
The IMDB API is documented here and you can see that it amounts to sending simple HTTP requests with some paramters and getting back some formatted data, possibly as a JSON string.
You will find libraries to help with doing those two things. Even if there are public domain wrappers for accessing IMDB I'd recommend attempting to use general purpose HTTP and JSON libraries - that's probably a better educational exercise.
I'm the author of the IMDB API you are dicussing ;) I limit requests to 30 per hour to stop people hammering. I have yet to have a legitimate reason to perform more requests than that. My suggestion to anyone is to write a batch script to perform 1 request every 2minutes and then leave it going for a few hours overnight. Then you only have to perform a request on demand whenever you add a new movie.