Develop Reference

Parsing a string into different variable types

Relatively new to programming here so I apologize if this is rather basic.
I am trying to convert string lines into actual variables of different types.
My input is a file in the following format:
double d1, d2 = 3.14, d3;
int a, b = 17, c, g;
global int gInt = 1;
final int fInt = 2;
String s1, s2 = "Still with me?", s3;
These lines are all strings at this point. I wish to extract the variables from the strings and receive the actual variables so I can use and manipulate them.
So far I've tried using regex but I'm stumbling here. Would love some direction as to how this is possible.
I thought of making a general type format for example:
public class IntType{
boolean finalFlag;
boolean globalFlag;
String variableName;
IntType(String variableName, boolean finalFlag, boolean globalFlag){
this.finalflag = finalFlag;
this.globalFlag = globalFlag;
this.variableName = variableName;
}
}
Creating a new wrapper for each of the variable types.
By using and manipulating I would like to then compare between the wrappers I've created and check for duplicate declarations etc'.
But I don't know if I'm on the right path.
Note: Disregard bad format (i.e. no ";" at the end and so on)

While others said that this is not possible, it actually is. However it goes somewhat deep into Java. Just search for java dynamic classloading. For example here:
Method to dynamically load java class files
It allows you do dynamically load a java file at runtime. However your current input does not look like a java file but it can easily be converted to one by wrapping it with a small wrapper class like:
public class CodeWrapper() {
// Insert code from file here
}
You can do this with easy file or text manipulations before loading the ressource as class.
After you have loaded the class you can access its variables via reflection, for example by
Field[] fields = myClassObject.getClass().getFields();
This allows you to access the visibility modifier, the type of the variable, the name, the content and more.
Of course this approach presumes that your code actually is valid java code.
If it is not and you are trying to confirm if it is, you can try to load it. If it fails, it was non-valid.

I have no experience with Java, but as far as my knowledge serves me, it is not possible to actually create variables using a file in any language. You'll want to create some sort of list object which can hold a variable amount of items of a certain type. Then you can read the values from a file, parse them to the type you want it to be, and then save it to the list of the corresponding type.
EDIT:
If I were you, I would change my file layout if possible. It would then look something like this:
1 2 3 4 //1 int, 2 floats, 3 booleans and 4 strings
53
3.14
2.8272
true
false
false
#etc.
In pseudo code, you would then read it as follows:
string[] input = file.Readline().split(' '); // Read the first line and split on the space character
int[] integers = new int[int.Parse(input[0])] // initialise an array with specefied elements
// Make an array for floats and booleans and strings the same way
while(not file.eof) // While you have not reached the end of the file
{
integers.insert(int.Parse(file.ReadLine())) // parse your values according to the size which was given on the first line of the file
}
If you can not change the file layout, then you'll have to do some smart string splitting to extract the values from the file and then create some sort of dynamic array which resizes as you add more values to it.
MORE EDITS:
Based on your comment:
You'll want to split on the '=' character first. From the first half of the split, you'll want to search for a type and from the second half, you can split again on the ',' to find all the values.

Check if array contains string

Ok, I have this program that is supposed to store information about CDs that are available in txt file. The file stores the data in format 'artist[tab]album' on the same line. What I want to do, is to have user input search query, and the program return if the CD is in the database. So let's say we have Green Day[tab]American Idiot in .txt file on some line, and when users types in Green, the programs checks that file and returns true. But my problem is, my current algorithm requires the string to completely match, instead of partial. So the users needs to type Green Day[tab]American Idiot to get true on the query. How to fix it? Thanks. I am sure it is something I don't see as beginner.
This is the part of the program that manages the search in the array Artists, that contains all the data currently stored in the .txt file
for (String e : artists){
if(Arrays.asList(e).contains(search)){
contains=true;
}

Why are you creating a list? You should use artist.contains(search) (yes, try to choose more relevant variable names). Also make sure you don't have null elements in the array or search is not null etc, but you can do something like:
for(String artist : artists) {
if(artist.toLowerCase().contains(search.toLowerCase()) {
contains = true;
// break; <- you may want to break here
}
}
You may want to toLowerCase() both of them for case-insensitive search.

Writing/reading array to file

I have an app that will create 3 arrays : 2 with double values and one with strings that can contain anything,alphanumeric,commas,points,anything the user might want to type or type by accident. The double arrays are easy.The string one i find to be tricky.
It can contain stuff like cake red,blue 1kg paper-clip,you get the ideea.
I will need to store those arrays somehow(i guess in a file is the easiest way),read them and get them back into the app whenever the user wants to.
Also,it would be well if they wouldn't be human readable,to only be able to read them thru my app.
What's the best way to do this ? My issue is,how can i read them back into arrays.Its easy to write to a file but then to get them back in the same array i put them in...How can i separate array elements for it not to split one element in two because it has a space or any other element.
Can i like,make 3 rows of text,each element split by a tab \t or something and when i read it each element will by split by that tab ? Will this be able to create any issues when reading ?
I guess i want to know how can i split the elements of the array so that it won't be able to ever read them wrong.
Thanks and have a nice day !

If you don't want the file to be human readable, you could usejava.io.RandomAccessFile.
You would probably want to specify a maximum string size if you did this.
To save a string:
String str = "hello";
RandomAccessFile file = new RandomAccessFile(new File("filename"));
final int MAX_STRING_BYTES = 100; // max number of bytes the string could use in the file
file.writeUTF(str);
file.skipBytes(MAX_STRING_BYTES - str.getBytes().length);
// then write another..
To read a string:
// instantiate again
final int STRING_POSITION = 100; // or whichever place you saved it
file.seek(STRING_POSITION);
String str = new String(file.read(MAX_STRING_BYTES));
You would probably want a use the beginning of the file to store the size of each array. Then just store all the values one by one in the file, no need for separators.

Custom parameters from text file

I am attempting to create a method which will either evaluate an expression saved as a string array or will return some sort of "equation object" to do the job. Essentially I have a String array which contains the following data:
equation[0] = side 1, equation[1] = operator (=,>,<), equation[2] = side 2.
Now, it is also important that I am able to use the side 1 and side two as variables in one of my objects. I am loading them in as such:
background = Ex Legionary;dexterity > 3;
Splitting at the semicolon for each condition. Any ideas? I have read that doing this directly may be impossible... if that is the case, any other ideas for how I can accomplish this? Thanks

How do you handle incomplete data in a Processing table?

I'm parsing a CSV using Processing's Table interface, but some rows are missing some data. I want to pull all the data available into my table, but I'm not sure how to handle the missing data--I keep getting NullPointerException when I loop over the table with dataTable.getInt on the missing values.
I don't have a background in statically typed languages, so I've no idea how to conditionally assign this data short of putting a separate try/catch around each assignment. Surely there's a better way?

Before calling dataTable.getInt method check if dataTable is not null like
if(dataTable != null) {
int my_nt = dataTable.getInt
}
//else skip since it is empty

Since your're using getInt--you should perform a regex search/replace ,<not numeric>, with ,<some int>,. In your case it may be as simple as replacing ,, with ,0,
Also, as Hassan suggests, double check that dataTable is not null.

Ok, so I figured out a way to do this:
First, call dataTable.makeNullEmpty(), which turns all the null values into empty strings.
Then, you can use a pattern like this:
String total_value = dataTable.getString(i, 4);
if(total_value.length() > 0) s.total_value = parseInt(total_value);
and you get assignment only if an int is there to be parsed.