Thread: Java read in + print to a file

Need to read in from a file. That file is a list of information like a name then next line can be a number. I need to take that info a output it into a file. So here i have the code to get the two file names but im starting to do the reading of the input file and it looks very wrong. I need to do a loop i think, how can i loop this to make it read in both strings and ints(I know the order). I still need to output it into a formatted way in the outfile but this loop is confusing me.

import java.io.FileReader;
import java.util.Scanner;
 
public class Standalonereport {
 
	public static void main(String[] args) {
 
		String fileName;
		String outFile;
 
 
		Scanner keyboardScanner = new Scanner(System.in);
 
		System.out.printf("Enter the file name: ");
 
		fileName = keyboardScanner.next();
 
		System.out.printf("Enter the output file name: ");
 
		outFile = keyboardScanner.next();
		//WORKING UP TO THIS POINT
 
		Scanner inputScanner;
		inputScanner = new Scanner(new FileReader(fileName));
		String s;
		s = inputScanner.nextLine();

im starting to do the reading of the input file and it looks very wrong.

Please explain why it's wrong.
What is in the the file?
What will be done with the lines read from the file?

Please edit your post and wrap your code with code tags:

[code]
**YOUR CODE GOES HERE**
[/code]

to get highlighting and preserve formatting.

Is there more that one data item on a line
or is each item on a separate line?

What is the program going to do with the data as it reads it in?


When will the program write data to the output file?

Is this what your are trying to do?
The program would have a loop that does the following
Reads in several lines of related data,
does some computations with the data from those lines
and writes out some line(s) in the report file
end of loop

Ok, what have you tried? Post the code you are having problems with and ask some questions about the problems.
Be sure to wrap the code in code tags.

Look at the API documentation for the Scanner class to see what methods might be useful
https://docs.oracle.com/javase/8/docs/api/index.html

Ok, that's a start. Does the loop read and print all the lines in the file?

Note: i is a poor name for a line of text. line would be a better name.

The complete try statement needs a catch clause at the end.
See the tutorial: https://docs.oracle.com/javase/tutor...tions/try.html

Read the API doc for the Scanner class to see how to use its constructor to read a file.

the output is just one line and its the name of the file

One of the constructors takes a String that contains the data that will be read with its methods. That is the one you used.

You used the wrong constructor for the Scanner class. Look at the API doc for the Scanner class to see what constructor.
There are some code examples in the API doc that show how to use the Scanner class to read from a file.

As another example, this code allows long types to be assigned from entries in a file myNumbers:
 
 
      Scanner sc = new Scanner(new File("myNumbers"));
      while (sc.hasNextLong()) {
          long aLong = sc.nextLong();
      }

Make sure the code in the catch block includes a call to the printStackTrace method:
e.printStackTrace();


Does the file have a long value as the first item to be read? If not the while loop will not run because it requires: hasNextLong() be true.
Change the while loop back to what was there in post#11 so that it reads lines, not long values

Nothing.

What do you mean by that?
You should get an exception message if the file is not found.


If filename does not have the path to the file, the file needs to be in the current directory for when the java program executes.

File name has to be the path?

Not necessarily. If the file is in the current directory when the program is executed, then just the filename will work.
If the file is somewhere else, then the path to file needs to be given to the program so it can find the file.

You should get an exception message if the program does not find the file.
If there is no exception message, then the program is finding the file and the problem probably is in the program.

The posted code does not show the statement that defines the Scanner class.
Post #15 has the proper definition using the File class in the Scanner constructor.

   Scanner inputScanner = new Scanner(new File(fileName));  // define Scanner to read from fileName

I'm glad you are making progress.