Changing Scanner input type

[mlad]

Hiya, I am reading data into a class contructor, using the keyboard with the Scanner class like this:

//removed

However I'd like also to like to be able to read in data from a text file using a method in another class. Is there a way to change the input type using (eg, using a parameter in the constructor) so that I can replace "System.in" with "new FileReader("H:\\...\\...\\file.txt")" when needed?

Thanks.

[PhHein]

Sure

public Person()
    {
    Scanner in = null;
    if(readfromFile){
        in = new Scanner(new File(path));
    } else {
        in = new Scanner(System.in);
    }

[mlad]

Of course, thanks very much for helping. I think I have realised it won't work however, because I need the constructor to be called repeatedly (while in.hasNextLine()) for the text file, meaning the scanner has to be declared outside of the constructor. Stupid me..

[karno]

what you mean that you can open file .txt in java??

[mlad]

No, I can just use the scanner to keep reading the next occurance of a string or int from it.

Incidentally, I'm now using the scanner to read details from the file and then use them as parameters for a constructor, but again it's not working.

//removed

I get an exception when it tries to create the new Demonstrator in the readDemonstratorData method. Is it possible to do it this way? I was trying to use a text file with the information in order seperated by spaces which didn't work, but putting them on seperate lines (and deleting the spaces) doesn't work either. I believe it is having trouble reading the strings. Any ideas? Help is appreciated!

payrollArray is a ArrayList field of the Payroll class, which is why I'm using the .add() method.

[PhHein]

First you should find out what you are reading:

public static void readDemonstratorData()
    {
        try
        {
            Scanner in = new Scanner(new FileReader("H:\\CSC1012\\Coursework\\Payroll\\DemonstratorData.txt"));
            
            while(in.hasNextLine())
            {
                String line = in.nextLine();
                System.out.println(line);
                //split the line i
            } 
        } catch(Exception e)
        {
            System.out.println(e.getMessage());
        }
    }

[mlad]

I tried that code and it helped me figure it out, it was working, I just hadn't written the text file correctly :s Thanks! However, it is calling the default constructor to the class instead of the one that takes parameters. The default one uses it's superclass Person which is similar but asks the user to enter different details.

//removed

So when I run the readDemonstratorData it opens the terminal and asks me to type the details in that way, instead of just entering the data it is reading.

[PhHein]

Now you've lost me. Post the code you have now and a few lines of the file you're trying to read.

[mlad]

Alllll the code? There are about 300 lines in 6 seperate classes :s, but I can if you need.

Basically, what I mean is it turns out the Scanner is correctly reading the file, as when I tried your suggested test code it reproduced the text exactly. The problem initally was that I had not written the text file properly.

Now, the demonstrator has two constructors, the first for manually entering the details (with no parameters, but it's own Scanner class for keyboard entry into the terminal), and the second with parameters. My code is using the first one despite having the parameters listed when it is intialised, but I need it to use the second.

It is concerning this code again:

//removed

[PhHein]

Split it up and see what's going on. Like this:

Scanner in = new Scanner(new FileReader("H:\\CSC1012\\Coursework\\Payroll\\DemonstratorData.txt"));
            
            while(in.hasNextLine())
            {

                String one = in.next();
                String two = in.next();
                System.out.println(one);
                System.out.println(two);
                // same for all c'tor parameters.
                Demonstrator newDemonstrator = new Demonstrator(one, two, in.nextInt(), in.nextInt(), in.nextInt(), in.next(), in.nextInt(), in.nextDouble(), in.nextDouble()); //**calls incorrect constructor here

But calling the wrong c'tor without exceptions looks like you've forgot to recompile one or more files.

[mlad]

Ok, I've tried that. It still prints out the correct information, but still the wrong constructor. I don't know what I've done here.

The Demonstrator class is a subclass to a Person class, and it's default constructor (the one that's being called, but I don't want) has a super(); call in it, but the second one (that I want to be used) doesn't. Could that have any effect?

I can't have forgotten to complie anything as I'm using BlueJ, you can't run anything if a part is not compiled.

[PhHein]

It might be compiled, but in an earlier version. What do I know? To help you you need to create an SSCCE

[mlad]

Ok, it's because some of the variables I was assigning were inherited from the superclass, and I didn't have a constructor that corresponded to the one I wanted to use from the Demonstrator. I had assumed that as Demonstrator was a subclass I could assign inherited variables without calling the super constructor. Thanks very much for helping!

[PhHein]

Glad it works now! Have fun.