Iterator next method must throw NoSuchElementException JAVA-S0146

This class implements the java.util.Iterator interface. However, its next() method is not capable of throwing java.util.NoSuchElementException.

This is a violation of the Iterator interface's contract, and will not work with code that expects next() to throw when the iterator is exhausted.

The next() method should be changed so it throws NoSuchElementException if is called when there are no more elements to return.

Example

This is a bad implementation and may mislead API consumers.

// Within iterator impl
@Override
public T next() {
    if (hasNext()) { ... } 
    else return null;
}

This implementation should be preferred:

@Override
public T next() {
    if (hasNext()) { ... }
    else throw NoSuchElementException();
}

If such behavior is a requirement, a more preferable alternative is to extend Iterator and create a new interface whose contract allows this:

public interface NonThrowingIterator extends Iterator { ... }

Otherwise, a NoSuchElementException must be thrown to ensure conformance with the Iterator API.