Is it legal to assign elements from an array list to a string like this?-CodePudding

When I put this into eclipse and ran it, it threw an exception "cannot convert from boolean to String" which is what I was expecting. However, the correct answer was "Emad". I don't see how this code would be able to run without an error.

It's assumed all essential imports and 'main' method are included

CodePudding user response：

This code will set size of aSet to 4:

import java.util.ArrayList;
import java.util.HashSet;
import java.util.List;

public class Test {
    public static void main(String[] args) {
        List<String> alist = new ArrayList<>();
        String unknown = "Emad";
        alist.add("Adam");alist.add("Emad");
        alist.add("Eve");alist.add("Jim");
        alist.add("Jim");alist.add("Eve");
        alist.add(unknown);
        HashSet<String> aSet = new HashSet<>(alist);
        System.out.println(aSet.size());
    }
}

Actually, any already used names will work for unknown as they will be filtered by set which can contain only unique values.