After asking about my previous work experiences, the interviewer asked just one single coding problem. No other skills were asked. The assessment was completely dependent on coding.

Coding Problem: Implement hasNext() and next() methods for a class that contains a collection of collections. (The main collection must not be null or empty, and sub-collections must not be null.)

Answer: I received several hints from the interviewer. I believe I didn't get the offer because I didn't finish the coding by myself, even though we discussed it nicely.

java public class CollectionOfCollections { private Iterator mainIter; private Iterator subIter;

CollectionOfCollections(Collection col) {
    mainIter = col.iterator();
    subIter = mainIter.next().iterator();
}

public boolean hasNext() {
    if (subIter.hasNext()) {
        return true;
    }

    while (mainIter.hasNext()) {
        subIter = mainIter.next().iterator();
        if (subIter.hasNext()) {
            return true;
        }
    }
    return false; // Added return statement
}

public Object next() throws NoSuchElementException {
    if (hasNext()) {
        return subIter.next();
    }

    throw new NoSuchElementException(); // Corrected syntax
}

}

Coding hasNext() and next() methods for a class that contains a Collection of Collections.

Requirements:

• The main collection must not be null or empty.
• Sub-collections must not be null.