Get the head set and tail set « TreeSet « Set « Collections

Return	Method	Summary
SortedSet<E>	headSet(E toElement)	Returns a view of the portion of this set whose elements are strictly less than toElement.
NavigableSet<E>	headSet(E toElement, boolean inclusive)	Returns a view of the portion of this set whose elements are less than (or equal to, if inclusive is true) toElement.
SortedSet<E>	tailSet(E fromElement)	Returns a view of the portion of this set whose elements are greater than or equal to fromElement.
NavigableSet<E>	tailSet(E fromElement, boolean inclusive)	Returns a view of the portion of this set whose elements are greater than (or equal to, if inclusive is true) fromElement.


  import java.util.Arrays;
import java.util.TreeSet;

public class Main {
  public static void main(String args[]) throws Exception {

    String elements[] = { "java2s.com", "C", "D", "G", "F" };
    TreeSet<String> set = new TreeSet<String>(Arrays.asList(elements));

    System.out.println(set.headSet("D"));
    System.out.println(set.tailSet("D"));
  }
}


[C]
[D, F, G, java2s.com]