如何从 SortedSet 子集<String>

Question

I have to write a code that makes it possible to delete all the words of a SortedSet starts with K.

import java.util.*;

public class Deleter {
    
    public static void deleteKWords(SortedSet<String> set) {
        set.subSet("K", "");
}
    }
    
}

I've heard that with a subSet can simple solved but i couldn't.

Answer 1

You can achive what you want by using Java 8 stream:

public static SortedSet<String> deleteKWords(SortedSet<String> set) {
   return new TreeSet<>(set
           .stream()
           .filter((s) -> !s.startsWith("K"))
           .collect(Collectors.toSet()));

}

Edit: Probably it will be more efficient to avoid creating new object every time and just modify the one you send to the method:

 public static SortedSet<String> deleteKWords(SortedSet<String> set) {
    set.removeAll(set
            .stream()
            .filter((s) -> s.startsWith("K"))
            .collect(Collectors.toList()));
    return set;

}

Answer 2

You can simply do this by combining subSet() and removeAll() methods:

public static void deleteKWords(SortedSet<String> set) {
    Set s = new TreeSet<>(set.subSet("K", "O"));
    set.removeAll(s);
}