The Collections Framework overview Blacklist

Has it ever bothered you when unknown people call you and try to impose their services? That can be annoying.

Let's try to solve the problem by using a blacklist. You should implement the filterPhones method that returns only the phone numbers that are not on the blacklist.

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import java.util.Scanner;
import java.util.stream.Collectors;

class CollectionUtils {

    public static Collection<String> filterPhones(Collection<String> phones,
                                                  Collection<String> blacklist) {
        // write your code here
        /*for (String phone : blacklist) {                       //===================
            if (phones.contains(phone)) {                       // basic for-each
                phones.remove(phone);                           \\ loop implementation
            }                                                    \\===================
        }*/
        
        //phones.removeAll(blacklist);                          //implementation using method from Collection
        
        //phones.removeIf(phone -> blacklist.contains(phone));    //lambda expression
           
        phones.removeIf(blacklist::contains);   // method reference

        
        return phones;
    }
}

/* Please, do not modify this I/O code */
class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);

        Collection<String> phones = Arrays.asList(scanner.nextLine().split("\\s+"));
        Collection<String> blockList = Arrays.asList(scanner.nextLine().split("\\s+"));

        Collection<String> nonBlockedPhones = CollectionUtils.filterPhones(
                new ArrayList<>(phones), new ArrayList<>(blockList));

        System.out.println(nonBlockedPhones.stream()
                .map(Object::toString)
                .collect(Collectors.joining(" ")));
    }
}