CODEWITHSUNDEEP
javasystem.in
Prakrit J
Prakrit J

Reputation: 11

System.in is not working with Scanner (NoSuchElementException)

So I'm creating a simple programme that contains arrays and such, and my programme compiles perfectly. However, when I run it and input the name of my file (flight), my programme gives me the error NoSuchElementException I delved deeper by finding out whether System.in was available through the following code:

System.out.println(System.in.available());

This is the rest of my relevant code:

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

public class FlightAirportController
{    
    public static void main(String[] args) throws IOException
    {
        Scanner input = new Scanner(System.in);
        System.out.print("Please name the Input File: ");
        System.out.println(System.in.available()); // checks if System.in is working: output is either 0 or 1.
        Scanner fileScanner = new Scanner(new File(input.next() + ".txt"));
        fileScanner.useDelimiter(", |\n");
    }
}

Upvotes: 1

Views: 331

Answers (2)

Rudra
Rudra

Reputation: 383

You are missing the file location.

import java.io.File;
import java.io.IOException;
import java.util.Scanner;

public class FlightAirportController
{
    public static void main(String[] args) throws IOException
    {
      Scanner input = new Scanner(System.in);
      System.out.print("Please name the Input File: ");
      System.out.println(System.in.available()); // checks if System.in is working: output is either 0 or 1.
      Scanner fileScanner = new Scanner(new File("C:\\Users\\..\\"+input.next() + ".txt"));
      fileScanner.useDelimiter(", |\n"); 
    }
}

NoSuchElementException Will come when you are calling next even if the Scanner has no next element to provide. Instead of file.next() use of file.hasNext() will be helpful.

Upvotes: 0

Виктор
Виктор

Reputation: 221

System.out.println(System.in.available());

This line always print zero, becose you can't write text so faster as needed.

1 will print in case you write text before this line work (very few milliseconds).

new File(input.next() + ".txt")

Scanner.next() return text until first space. If file name contains space you mast set delimeter with Scanner.useDelimiter(pattern).

Scanner.next throws NoSuchElementException - if no more tokens are available.

Solution:

use method Scanner.hasNext() - return true if inputStream contains character to read/ false - in otherwise.

If you need read Line, use Scanner.hasNextLine() and Scanner.nextLine()

Upvotes: 1

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