How to Fix Error: No Such Element Exception While Using Scanner in Java

This tutorial will demonstrate solving the NoSuchElementException error while using the Scanner in Java.

No Such Element Exception While Using Scanner in Java

The Scanner class is used to get the user input in a Java program. It uses several utility methods like next(), nextInt(), etc.

When working with these methods, the Scanner can throw a NoSuchElementException error in Java. The reason for these exceptions are given below:

1. Suppose we have two Scanner objects for getting user input; if we close one Scanner and get the input from the other one, it will throw the NoSuchElementExcpetion. This is because when we close one Scanner, it will close the Input Stream; that is why the other Scanner cannot read from the same Input Stream because the close() method also closes the System.in input stream.

   Here is an example:

   package delftstack;
   
   import java.util.*;
   
   public class Example {
     public static void main(String args[]) {
       String DemoString = "Hello, This is delftstack.com";
   
       Scanner DemoScanner1 = new Scanner(System.in);
       Scanner DemoScanner2 = new Scanner(System.in);
   
       DemoScanner1.close();
       DemoScanner2.next();
     }
   }
   

   The code above will throw the NoSuchElementException. See output:

   Exception in thread "main" java.util.NoSuchElementException
   	at java.base/java.util.Scanner.throwFor(Scanner.java:937)
   	at java.base/java.util.Scanner.next(Scanner.java:1478)
   	at delftstack.Example.main(Example.java:13)
   

   To solve this issue, we can use just one Scanner. This also applies if one Scanner is used in one method and the other in another method.

   The close() method will close all the input streams.

2. While using Scanner, we are reading the line, and if there is no line left to read, it will throw the NoSuchElementException. See example:

   package delftstack;
   
   import java.util.*;
   
   public class Example {
     public static void main(String args[]) {
       String DemoString = "Hello, This is delftstack.com";
   
       Scanner DemoScanner1 = new Scanner(DemoString);
   
       System.out.println(DemoScanner1.nextLine());
       System.out.println(DemoScanner1.nextLine());
     }
   }
   

   To solve the issue, we use the hasNextLine() to check if the Scanner has the next line. It returns true if the Scanner has the next line; otherwise, it returns false.

   See example:

   package delftstack;
   
   import java.util.*;
   
   public class Example {
     public static void main(String args[]) {
       String DemoString = "Hello, This is delftstack.com";
   
       Scanner DemoScanner1 = new Scanner(DemoString);
       while (DemoScanner1.hasNextLine()) {
         System.out.println(DemoScanner1.nextLine());
       }
     }
   }
   

   The output for this code is:

   Hello, This is delftstack.com