Scanner Nosuchelementexception

java.util.NoSuchElementException - Scanner reading user input

This has really puzzled me for a while but this is what I found in the end.

When you call, sc.close() in first method, it not only closes your scanner but closes your System.in input stream as well. You can verify it by printing its status at very top of the second method as :

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

So, now when you re-instantiate, Scanner in second method, it doesn't find any open System.in stream and hence the exception.

I doubt if there is any way out to reopen System.in because:

public void close() throws IOException --> Closes this input stream and releases any system resources associated with this stream. The general contract of close is that it closes the input stream. A closed stream cannot perform input operations and **cannot be reopened.**

The only good solution for your problem is to initiate the Scanner in your main method, pass that as argument in your two methods, and close it again in your main method e.g.:

main method related code block:

Scanner scanner = new Scanner(System.in);  

// Ask users for quantities 
PromptCustomerQty(customer, ProductList, scanner );

// Ask user for payment method
PromptCustomerPayment(customer, scanner );

//close the scanner 
scanner.close();

Your Methods:

 public static void PromptCustomerQty(Customer customer, 
                             ArrayList<Product> ProductList, Scanner scanner) {

    // no more scanner instantiation
    ...
    // no more scanner close
 }

 public static void PromptCustomerPayment (Customer customer, Scanner sc) {

    // no more scanner instantiation
    ...
    // no more scanner close
 }

Hope this gives you some insight about the failure and possible resolution.

NoSuchElementException in java.util.Scanner

NoSuchElementException is thrown from Scanner.next() if you are trying to read data when you have reached the end of the data stream.

Instead of:

sc.next();
...

use:

while(! sc.hasNext()) { }
sc.next();
...

Scanner.hasNext() checks if there is any more data to read, and the while loop waits until there is more data to read before continuing.

NoSuchElementException with Java.Util.Scanner

NoSuchElementException Thrown by the nextElement method of an Enumeration to indicate that there are no more elements in the enumeration.

http://docs.oracle.com/javase/7/docs/api/java/util/NoSuchElementException.html

How about this :

if(input.hasNextInt() )
     number1 = input.nextInt(); // if there is another number  
else 
     number1 = 0; // nothing added in the input 

Fixing java.util.NoSuchElementException for Scanner

Stop the madness of closing a Scanner linked to System.in! It will close the underlying stream (System.in), causing any other attempt to read from that Stream to throw an exception.

Yes you will get a warning, but it is safe to ignore that warning, or you can add

@SuppressWarnings("resource")
Scanner in = new Scanner(System.in);

To avoid it.

Remember, if you didn't open a resource, you shouldn't close it. Let the JVM close it when it terminates the program.

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This also includes creating a Scanner(System.in) inside a try with resources block:

try(Scanner in = new Scanner(System.in)){
   //Code... 
} 

This will implicitly close the stream at the end of the block.

From the Java tutorials:

The try-with-resources statement ensures that each resource is closed at the end of the statement.

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Also you have several Scanner objects reading from System.in, which is bad practice. I would pass them to your methods as a parameter:

public static double solvingForMass(Scanner in) {

    System.out.println("Please enter a value for force.");
    double f = in.nextDouble();

    System.out.println("Please enter a value for acceleration.");
    double a = in.nextDouble();

    return f / a;

}

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Also just a note that if you are ever doing the structure of:

if(someBool)
   return true;
else
   return false;

It can be simplified to just

return someBool

So your isValidChoice() method can be simplified to:

public static boolean isValidChoiceChar(String c) {
     return c.compareTo("Y") == 0 || c.compareTo("N") == 0;
}

Although note you can use the equals() and equalsIgnoreCase()methods to compareString`'s

Scanner next() throwing NoSuchElementException for some online compilers

This exception gets thrown because there are no more elements in the enumeration.

See the documentation:

Thrown by the nextElement method of an Enumeration to indicate that
there are no more elements in the enumeration.

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Some online IDEs don't allow user input at all, in which case the exception will get thrown as soon as you try to read user input.

1. It works on TutorialsPoint IDE because it allows user input.
2. It doesn't works on codechef and compilejava IDEs because these IDEs does not support user input.

However there's secondary way to add user input on codechef. Just tick mark on Custom Input checkbox and provide any input. It will then compile.

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Another reason for this exception, i.e. there simply not being more user input, can be handled by, before calling s.next(), just checking s.hasNext() to see whether the scanner has another token.

  Scanner s = new Scanner(System.in);
  System.out.print("Enter name: ");
  String name = null;
  if(s.hasNext())
      name = s.next();
  System.out.println("Name is " + name);

how to fix : Exception in thread main java.util.NoSuchElementException: No line found

You're creating two Scanner objects based on System.in.

Each Scanner will read from System.in and consume some of its input. That means that the first one might have already read some things into its buffer when you created the second one.

The short answer is: never create multiple Scanner objects based on the same parameter, simply continue using the existing scanner. For example this would fix your issue:

public static void main(String[] args) {  
     Scanner myScanner = new Scanner(System.in);
     String userName = myScanner.nextLine(); 
     System.out.print("Username is: " + userName);
    
    
     String number = myScanner.nextLine();
     // ... rest of your code ...

how to solve NoSuchElementException Error in Scanner of Java?

private static void gamePlay(boolean isPlaying) {

    while (isPlaying) {

        System.out.println("Choose a, d , s or w for movement:");
        Scanner sc = new Scanner(System.in);
        String choice = sc.next();
        // code for movement of player according to a or s or d or w
        switch (choice) {
            case "a":
                // Some code here
                // move -x
                break;

            case "d":
                // Some code here
                // move +x

                break;

            case "w":
                // Some code here
                // move +y

                break;

            case "s":
                // Some code here
                // move -y

                break;
            case "q":
                //quit
                sc.close();
                isPlaying = false;
                break;

            default:
                break;
        }

    }
}

NoSuchElementException on Scanner, how do i get rid of it?

Don't invoke s.next() twice, but assign the result of the first call to a variable:

while (s.hasNext()) {
    String value = s.next();
        
    if(value.contains(",")) {
        String str = value.replaceAll("[^a-zA-Z0-9]", "");
        List<String> brokenSentence = Arrays.asList(str.split(","));
        writer.write(brokenSentence +"\n");
    } else {
        String edited = value.replaceAll("[^a-zA-Z0-9]", "");
        writer.write(edited +"\n");
    }
}

Continuously calling s.next() will keep consuming values from the scanner. Those values are not necessarily there because you have only checked for the presence of one value using s.hasNext().

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