Working with Subsets : TreeSet « Collections « Java Tutorial

1. Java Tutorial
2. Collections
3. TreeSet

Since a TreeSet is ordered, its subset is also ordered. The two that are simplest to explain are headset() and tailSet():

public SortedSet headSet(Object toElement)
public SortedSet tailSet(Object fromElement)

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

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

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

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

[A, C]
[A, C, D, F, G]