How to solve java.util.NoSuchElementException in Java? Example

How to fix java.util.NoSuchElementException in Java

java.util.NoSuchElementException is a RuntimeException that can be thrown by different classes in Java like Iterator, Enumerator, Scanner, or StringTokenizer. All of those classes have a method to fetch the next element or next tokens if the underlying data structure doesn't have any element Java throws "java.util.NoSuchElementException". The most common example of this is iterating over hashmap without checking if there is an element or not and that's why it's advised to use hashNext() before calling next() on Iterator. In this Java tutorial we will what causes NoSuchElementException in Java and how to avoid it completely.

Cause of Exception in thread "main" java.util.NoSuchElementException in Java:

here are possible cause of java.util.NoSuchElementException in Java:

1) As per Javadoc NoSuchElementException is thrown if you call the nextElement() method of Enumeration and there is no more element in Enumeration. below code will throw java.util.NoSuchElementException because the Enumeration of hashtable is empty.

public class NoSuchElementExceptionDemo{

    public static void main(String args[]) {

        Hashtable sampleMap = new Hashtable();

        Enumeration enumeration = sampleMap.elements();

        enumeration.nextElement();  //java.util.NoSuchElementExcepiton here because enumeration is empty

    }

}

Output:

Exception in thread "main" java.util.NoSuchElementException: Hashtable Enumerator

        at java.util.Hashtable$EmptyEnumerator.nextElement(Hashtable.java:1084)

        at test.ExceptionTest.main(NoSuchElementExceptionDemo.java:23)

And, If you are new to the Java world then I also recommend you go through these Java Programming courses to learn Java in a better and more structured way. This is one of the best and up-to-date courses to learn Java online.

Here is another example of a java.util.NoSuchElementException which will be thrown because we are calling next() method of Iterator which doesn't contain any element:

public class NoSuchElementExceptionExample {

    public static void main(String args[]) {

        HashMap sampleMap = new HashMap();

        Iterator itr = sampleMap.keySet().iterator();

        itr.next();  //java.util.NoSuchElementExcepiton here because iterator is empty

    }

}

Exception in thread "main" java.util.NoSuchElementException

        at java.util.HashMap$HashIterator.nextEntry(HashMap.java:796)

        at java.util.HashMap$KeyIterator.next(HashMap.java:828)

        at test.NoSuchElementExceptionExample.main(ExceptionTest.java:22

In order to avoid these NoSuchElementException always call Iterator.hasNext() or Enumeration.hasMoreElements() before calling next() or nextElement() method.

java.util.StringTokenizer can also throw NoSuchElementException if there is no more token or element and you call the nextToken() or nextElement() method. 

Here is an example of java.util.NoSuchElementException while using StringTokenizer in Java

import java.util.StringTokenizer;

public class StringTokenizerDemo {

    public static void main(String args[]) {

        StringTokenizer tokenReader = new StringTokenizer("", ":");

        System.out.println(tokenReader.nextToken());

    }

}

Exception in thread "main" java.util.NoSuchElementException

        at java.util.StringTokenizer.nextToken(StringTokenizer.java:332)

        at test.ExceptionTest.main(StringTokenizerDemo.java:23)

To get rid of this exception while using Stringtokenizer call hasMoreTokens() or hashMoreElements() before proceeding to call nextToken() or nextElement().

here is modified code that will not throw java.util.NoSuchElementException even if there is no more element because it's safeguarded forms hashMoreTokens() method which returns true if there is more tokens available.

 StringTokenizer tokenReader = new StringTokenizer("", ":");

 while (tokenReader.hasMoreTokens()) {

   System.out.println(tokenReader.nextToken());

 }

We have seen possible causes of java.lang.NoSuchElementException in Java can come while using Iterator or Enumeration or StringTokenizer. Best way to fix NoSuchElementException in java is to avoid it by checking Iterator with hasNext(), Enumeration with hashMoreElements() and StringTokenizer with hashMoreTokens().

Some Java Tutorials you may like:

What is a volatile variable in Java

How to use a transient variable in Java

How to convert ArrayList into HashSet in Java

What is the blank final variable in Java

Difference between a static method and Static block in Java

Difference between fail-safe and fail-fast Iterator in Java

How to solve Invalid Column Index Exception in Java JDBC

Difference between ClassNotFoundException and NoClassDefFoundError

Now lastly one question for you? When was the last time you used StringTokenizer? Do you prefer to use String.split() or StringTokenizer?