Reading From File

Code:

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                File f = new File("F:/" + date + ".txt");
                if (!f.exists()) {
                        System.out.println("file not found !");
                        System.exit(1);
                }
                int lines = 0;
                @SuppressWarnings("resource")
                Scanner scan = new Scanner(f);
                while (scan.hasNext()) {
                        System.out.println(scan.nextLine());
                        lines++;

                }
                System.out.println(lines);
                scan.reset();
                int sum = 0;
                int arr[] = new int[lines];
                for (int i = 0; i < lines; i++) {
                        arr[i] = Integer.valueOf(scan.nextLine()).intValue();

                        sum += arr[i];
                }
                System.out.println(sum);

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the date.txt file contains numbers form 1-100, I want to sum and copy them in arr[] but I get noSuchElementException ... Is it why, after counting the lines, the pointers goes to 100th line and then starts form there again??? I have reset the point though ...

Resetting a scanner does not reset the FileInputStream used (as you could've known by reading the API documentation of the Scanner class). I'd use a List<String> for this purpose though, not a fixed size array ...

kind regards,

Jos

I was just testing .. ok I will use linke list .. now what should I do to sum those numbers ?

If all you want to do is sum those numbers, I shouldn't use arrays nor a List<String>; I'd just keep an int sum= 0; ready and add those numbers to it ...

kind regards,

Jos

how can I reset the pointer ?

Quote:

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Originally Posted by allaudin

how can I reset the pointer ?

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What pointer?

kind regards,

Jos

file input pointer to the start of the file ...

thanks I have done it wiht randomAccessFile ... thanks josAh ....

Quote:

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Originally Posted by allaudin

thanks I have done it wiht randomAccessFile ... thanks josAh ....

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Why do you want to read that file more than once? You can read those numbers (and add them) while reading the file ...

kind regards,

Jos

yes I can ... I was just learning how to read it more than once ..

Well simply opening a new FileInputStream also works, although when using a Scanner that would also mean creating a new Scanner. Which functionally makes sense IMO since you want to scan a new file to get fresh data - even if it is the exact same one as the previous time.

What if you wanted to actually system.out.println the number of lines (along with those) with a method call? Would you use another class to call getter method code like this:

int numberOfLines = 0;

//Loop through the lines of text, reading each line of text and stop when a
//null value is reached (if there is no more lines in the text file, Java
//returns a value of null):
while((aLine = bf.readLine()) != null){
numberOfLines++;//increment a counter called numberOfLines
}
bf.close();//flush the temporary memory buffer called bf
return numberOfLines;//return the number of lines
}

private String getLines(String numberOfLines){
lines = numberOfLines;
return "File has " + lines;
}//end of getLines method


/*
* Because the getLines method has been set to private, we will need to
* add a non-private getter method to pass the number of lines from the
* private numLines method above.
*
* Because this getter method is not private, the method in the
* FileData.java class will call for the number of lines passed into this
* getter method, rather than directly from the private getLines method:
*/
String giveLines(int aLines){
lines = this.getLines();//The this Java keyword "this"
//means "this class", rather than another class that may have the
//same method name. It avoids any confusion.
return lines;
}