java.util.NoSuchElementException - Scanner reading user input

Question

I\'m new to using Java, but I have some previous experience with C#. The issue I\'m having comes with reading user input from console.

I\'m running into the \"java.u

Answer 1

the reason of the exception has been explained already, however the suggested solution isn't really the best.

You should create a class that keeps a Scanner as private using Singleton Pattern, that makes that scanner unique on your code.

Then you can implement the methods you need or you can create a getScanner ( not recommended ) and you can control it with a private boolean, something like alreadyClosed.

If you are not aware how to use Singleton Pattern, here's a example:

public class Reader {
    
    
    private Scanner reader;
    private static Reader singleton = null;
    private boolean alreadyClosed;
    
    private Reader() {
        alreadyClosed = false;
        reader = new Scanner(System.in);
    }
    
    public static Reader getInstance() {
        if(singleton == null) {
            singleton = new Reader();
        }
        return singleton;
    }
    
    public int nextInt() throws AlreadyClosedException {
        if(!alreadyClosed) {
            return reader.nextInt();
        }
        throw new AlreadyClosedException(); //Custom exception
    }
    
    public double nextDouble() throws AlreadyClosedException {
        if(!alreadyClosed) {
            return reader.nextDouble();
        }
        throw new AlreadyClosedException();
    }
    
    public String nextLine() throws AlreadyClosedException {
        if(!alreadyClosed) {
            return reader.nextLine();
        }
        throw new AlreadyClosedException();
    }
    
    public void close() {
        alreadyClosed = true;
        reader.close();
    }   
}