Scanner only reads 2nd line of text file

Question

Code

public class Login {

    private String nickname;
    private static String line;

    public Login(String nickname) throws IOException {
        this.nickname = nickname;

        try {
            Scanner input = new Scanner(new File(nickname + ".acc"));
            while (input.hasNextLine()) {
                line = input.nextLine();
            }
            input.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    public static void main(String[]args) throws IOException {
        new Login("example");
        System.out.println(line);
    }
}

I have a problem. If I use this code, my output will only say 34567. But my text file contains:

example
34567

How do I fix it, and is it possible that the scanner outputs both lines of text from the textfile to separate strings?

Answer 1

Your problem lies in this bit of code:

// loop until the input has no more lines
while (input.hasNextLine()) {
    // PLACE the current line from the file into the line variable
    line = input.nextLine();
}

You will always be overwriting the line variable with the last line read. This leads to your program only storing the last line of the file.

The simplest fix is to just append the line to the existing variable.

// loop until the input has no more lines
while (input.hasNextLine()) {
    // APPEND the current line from the file into the line variable
    line += input.nextLine() + "\n"; // append a newline...
}

You also will need to initialize the line variable, Above your while loop you can just initialize it to an empty string

line = "";
while(...) ...

This will lead to 1 extra new line in your line variable however. A better way would be to just read the file contents instead of using a scanner, see this question for more information How do I create a Java string from the contents of a file?

Answer 2

line = input.nextLine();

Here you are overriding the line you read before. You could just add the new line to your line variable like this:

line += input.nextLine();

If you want a line break after each line you read, you can add the newline character at the end of each line:

line += input.nextLine() + "\n";

Answer 3

The problem here is with your while loop. while (input.hasNextLine()) tells the program to run the loop until the Scanner reaches the last line in the file. Since the only line of code within the loop sets the value of line to equal the next line of text in the file, it will simply keep changing the value of line until it reaches the last line. The simplest solution to fix this would be to move System.out.println(line) to be inside of the while loop, following line = input.nextLine().

Alternatively, if you wish to keep the println() method within your main method, you could have your while loop store each line of text into an ArrayList<String> and then have a for loop in the main method to iterate through it and print each element, but that would require making the code more complex than simply moving one line of code and would result in the exact same output anyway.

Answer 4

From your comment:

can I store both lines of my string 'line', into two strings?

I made this, using a String array. You should use a List because of performance, as @ug_ suggested

The following example shows how to use the String array. I'll suggest you to try using a List yourself, so you learn something new.

The last part is commented, since, as you said you're a Java starter you're maybe be more familiar with a for-loop instead a for-each loop, both for loops in the code work exactly the same way. I recommend you to learn about both them too.

Edit

As of @ug_ comment I made a new approach which ended being an edit to his own answer. (So his answer is actually the correct one). It adds a new line \n after it reads each line on the file, then it splits by this line break and stores it into an array, after that it just prints it out:

import java.util.Scanner;
import java.io.*;
public class Login {

    private String nickname;
    private static String lines[];

    public Login(String nickname) throws IOException {
        this.nickname = nickname;

        try {
            Scanner input = new Scanner(new File(nickname + ".acc"));
            String line = "";
            while (input.hasNextLine()) {
                line += input.nextLine() + "\n"; //Add a new line to our string
            }
            lines = line.split("\n"); //Split the string and store it into the array
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    public static void main(String[]args) throws IOException {
        new Login("example");
        for (String s : lines) { //print each element of the array.
            System.out.println(s);
        }
        /*for (int i = 0; i < lines.length; i++) {
            System.out.println(lines[i]);
        }*/
    }
}

The output is:

example
34567