Parsing a string into different variable types

Question

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)

Answer 1

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.

Answer 2

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.