read from two separate text files and write into one

Question

need to combine two text files of girl names and boy names into one text file. the new file has to have the boy names and girl names separated into two lists of each gender, and we dont know how many names each file will have. the program runs but gets stuck in an infinite loop

import java.io.FileNotFoundException;
import java.io.FileReader;
import java.io.PrintWriter;
import java.util.Scanner;

public class NameTester 
{
    public static void main(String args[]) throws FileNotFoundException
    {
        Scanner userIn = new Scanner(System.in);
        System.out.println("Enter file name for boys name file: ");
        String boyFile = userIn.next();
        System.out.println("Enter file name for girls name file: ");
        String girlFile = userIn.next();
        userIn.close();

        Scanner boyIn = new Scanner(new FileReader(boyFile));
        Scanner girlIn = new Scanner(new FileReader(girlFile));

        PrintWriter out = new PrintWriter("names.txt");
        out.print("Boys Names:                  Girls Names: ");
        int count = 1;
        while(boyIn.hasNextLine() || girlIn.hasNextLine());
        {
            String b = boyIn.next();
            String g = girlIn.next();
            out.print(count + " " + b + "                   " + count + " " + g);
            count++;
        }

        boyIn.close();
        girlIn.close();
        out.close();
   }
}

Note that nowadays you should read/write files using Java **NIO**, revolving around the classes `Path`, `Paths` and `Files`. Also note that resources like `Scanner` should be managed using *try-with-resources*. — Zabuzard, Mar 05 '18 at 16:00
See [What's the difference between next() and nextLine() methods from Scanner class?](https://stackoverflow.com/questions/22458575/whats-the-difference-between-next-and-nextline-methods-from-scanner-class) — Zabuzard, Mar 05 '18 at 16:01
Good point, otherwise you will call `next()` on a file that has no input anymore due to the *logical or* in the condition. — Zabuzard, Mar 05 '18 at 16:03
@Berger no matter if i use next() or nextLine() it always just gets stuck looping — jacobc55, Mar 05 '18 at 16:25
@jacobc55 Then you will have to handle that. If you try to read from a file after you've read through to the end, an exception will be thrown. — Johnny Mopp, Mar 05 '18 at 16:37

score 2 · Answer 1 · answered Mar 05 '18 at 16:30

This line is an empty while loop that will run forever:

while(boyIn.hasNextLine() || girlIn.hasNextLine());

Get rid of the semicolon at the end:

while(boyIn.hasNextLine() || girlIn.hasNextLine()) // <- NO SEMICOLON
{
    ....
}

I haven't checked for other logic errors in your program, but this should get rid of the infinite loop.

read from two separate text files and write into one

1 Answers1