This is from the task:

Select Comparator<> as the implemented interface.
Inside the anonymous class, override the comparison method, namely compare.
To get the last name from a string, split the string on a space using split and take the second part of the split.

import java.util.stream.Collectors;

public class Practicum {
    public static void main(String[] args) throws Exception {
        List<String> people = new ArrayList<>(List.of(
                "Maria Zue",
                "Anna Darkness",
                "Kirl Filimon",
                "Eva Pink"
        ));

        Comparator<String> comparator = ... // <-- write your code here
        };

        Collections.sort(people, comparator);

        System.out.println(people);
    }
}


// My desicion wasn't correct:
Comparator<String> comparator = new Comparator<>() { // <-- write your code here
@Override
public int compare(String o1, String o2) {
    return o1.split(" ")[1].compareTo(o2.split(" ")[1]);
    }
};

>Solution :

You are on the right path, you just need to compare the length of the strings and not the strings themselves:

Comparator<String> comparator = new Comparator<>() {
    @Override
    public int compare(final String o1, final String o2) {
        return Integer.compare(o1.split(" ")[1].length(), o2.split(" ")[1].length());
    }
};

Using lambda expression you can simplify the above aand rewrite it as:

Comparator<String> comparator = (o1, o2) -> Integer.compare(o1.split(" ")[1].length(), o2.split(" ")[1].length());

the above can get further refactored using Comparator.comparingInt

Comparator<String> comparator = Comparator.comparingInt(o -> o.split(" ")[1].length());