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morningpost

Tue Jan 25, 2011 9:05 pm


Java File Input (Character by Character)

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Hi there,

I just need to know how to read in from a text file character by character in Java.

I've tried using Scanner, InputStreamReader, DataInputStream, FileInputStream ... but I'm obviously going wrong somewhere. I just can't seem to be able to read in from the file character by character. The file is supposed to be a maze, with the first two numbers representing # of columns and # of rows. I want to read in character by character so I can place the characters into a 2D array in my program.

The textfile looks something like this (legend: '#' - wall, '.' - open space, 'o' - start, '*' - finish):

7 4 
#######
# . . . #o#
# *#. . . #
#######

^ So, these are the types of characters I want to read in one by one :)

If someone could help with this, that'd be great! Thanks! :D


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Tony

Tue Jan 25, 2011 9:19 pm


RE:Java File Input (Character by Character)

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How did you try using Scanner?

http://download.oracle.com/javase/6/docs/api/java/util/Scanner.html


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morningpost

Tue Jan 25, 2011 9:27 pm


Re: RE:Java File Input (Character by Character)

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How did you try using Scanner?

http://download.oracle.com/javase/6/docs/api/java/util/Scanner.html

I tried using the Scanner this way, but it won't read in character by character ...

File file = new File("maze1.txt");
try {
            s = new Scanner(file);

            int columns = s.nextInt();
            int rows = s.nextInt();
            String grid = new String[rows][columns];

            while (s.hasNext()) {
                    int r = 0;
                    int col = 0;
                    String square = s.next();
                    grid[r][col] = square;

                    r++;
                    col++;
            } 
}catch (FileNotFoundException e) {
            System.out.println("File cannot be found! " + e);
}


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Tony

Tue Jan 25, 2011 9:40 pm


RE:Java File Input (Character by Character)

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What does #next() return..?
http://download.oracle.com/javase/6/docs/api/java/util/Scanner.html#next()

[code]
String grid = new String[rows][columns]; 
[/code]
Wait, what does this mean?


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RandomLetters

Tue Jan 25, 2011 9:43 pm


RE:Java File Input (Character by Character)

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You can use toCharArray() method to convert string to an array of characters.


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morningpost

Tue Jan 25, 2011 9:49 pm


Re: RE:Java File Input (Character by Character)

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What does #next() return..?
http://download.oracle.com/javase/6/docs/api/java/util/Scanner.html#next()



next () returns the entire first row and then nothing else :\

oh, sorry. It's suppose to be String [][] grid = new String[rows][columns]. My mistake.


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Tony

Tue Jan 25, 2011 9:53 pm


Re: RE:Java File Input (Character by Character)

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next () returns the entire first row and then nothing else :\
Yup, sounds like that's not the method that you are looking for. Find one that returns the type that you want.


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ProgrammingFun

Tue Jan 25, 2011 10:21 pm


RE:Java File Input (Character by Character)

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Why don't you use BufferedReader to read one line at a time. This line can be saved in a String from which you can use .charAt() to extract characters?


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Tony

Tue Jan 25, 2011 10:38 pm


RE:Java File Input (Character by Character)

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Or use a Scanner to scan for the next character token and use that directly.


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RandomLetters

Tue Jan 25, 2011 11:24 pm


Re: RE:Java File Input (Character by Character)

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Or use a Scanner to scan for the next character token and use that directly.

How do you do that?  next() Set delimiter to ""?  I could not find a nextChar() method or similar, which is interesting (so there must be an obvious way)