How to read an arbitrary amount of lines from standard input using Scanner in java

I'm looking to scan standard input and write what is inputted into a file.

Currently, my code looks like this

import java.util.*;
import java.io.*;

public class ShoppingList {

    public static void main(String[] args) {
        if (args.length != 1) {
            System.err.println("Invalid number of arguments.");
            return;
        }

        String outputFile = args[0];

        try {
            Scanner scanIn = new Scanner(System.in);
            File fileOut = new File(outputFile);
            PrintWriter myWriter = new PrintWriter(fileOut);
            fileOut.createNewFile();

            while (true) {
                String nextLine = scanIn.nextLine();
                if (nextLine.equals("")) {
                    break;
                }
                myWriter.write(nextLine + "\n");
            }
            myWriter.close();
        } catch (IOException e) {
            System.err.println("IOException");
            return;
        }
        
    }
}

Currently, my code leaves a blank line between the end of the input stream and the end of the program. Link Is there any way to get rid of that line? Thanks!

Don't add the newline (\n) to the end of the input when you write to file such as:

myWriter.write(nextLine + "\n");

Instead add it to the file before you add the User input string to file. Yes, this would add a blank line before the first User input line is written to file so you need a means to determine if a line has already been written to the file. There are a number of ways you can do this, a counter, a boolean flag, etc.

Using a Boolean Flag:

public class ShoppingList {
public static void main(String[] args) {
if (args.length != 1) {
System.err.println("Invalid number of arguments.");
return;
}
String outputFile = args[0];
try {
Scanner scanIn = new Scanner(System.in);
File fileOut = new File(outputFile);
java.io.PrintWriter myWriter = new java.io.PrintWriter(fileOut);
fileOut.createNewFile();
// Boolean Flag to determine if first line is written to file.
boolean firstLineWritten = false; 
while (true) {
String nextLine = scanIn.nextLine().trim();
if (nextLine.equals("")) {
// Nothing provided by User - Close the file.
break;
}
// If a first line has been written...
if (firstLineWritten) {
// Add a system line separator to the file line previously written.
myWriter.write(System.lineSeparator());
}
// Add User Input to file (no newline character added)
myWriter.write(nextLine);
// Write the User input to the file right away!
myWriter.flush(); 
// Flag the fact that the first line is written.
firstLineWritten = true; 
}
myWriter.close();
} catch (IOException e) {
System.err.println("IOException");
}
}
}

Using a Counter:

public class ShoppingList {
public static void main(String[] args) {
if (args.length != 1) {
System.err.println("Invalid number of arguments.");
return;
}
String outputFile = args[0];
try {
Scanner scanIn = new Scanner(System.in);
File fileOut = new File(outputFile);
java.io.PrintWriter myWriter = new java.io.PrintWriter(fileOut);
fileOut.createNewFile();
// A counter to determine if first line is written to file. 
int lineCounter = 0; 
while (true) {
String nextLine = scanIn.nextLine().trim();
if (nextLine.equals("")) {
// Nothing provided by User - Close the file.
break;
}
// If a first line has been written...
if (lineCounter > 0) {
// Add a system line separator to the file line previously written.
myWriter.write(System.lineSeparator());
}
// Add User Input to file (no newline character added)
myWriter.write(nextLine);
// Write the User input to the file right away!
myWriter.flush(); 
// Increment counter to the fact that the first line is written.
lineCounter++; 
}
myWriter.close();
} catch (IOException e) {
System.err.println("IOException");
}
}
}