Creating a TreeSet : TreeSet « Collections « Java Tutorial

The first two constructors create empty tree sets:

public TreeSet()
public TreeSet(Comparator comp)

Pass along a custom Comparator to the constructor that will be used to keep elements ordered.

Once the TreeSet is created, you cannot change the comparator.

import java.util.Collections;
import java.util.Set;
import java.util.TreeSet;

public class MainClass {
  public static void main(String args[]) throws Exception {
    String elements[] = { "A", "C", "D", "G", "F" };
    Set set = new TreeSet(Collections.reverseOrder());
    for (int i = 0, n = elements.length; i < n; i++) {
    System.out.println(((TreeSet) set).comparator());
[G, F, D, C, A]

9.22.1.TreeSet Class
9.22.2.Creating a TreeSet
9.22.3.Get Synchronized Set from TreeSet
9.22.4.Copy all elements in TreeSet to an Object Array
9.22.5.Get Head Set from Java TreeSet
9.22.6.Get lowest and highest value stored in TreeSet
9.22.7.Get Size of TreeSet
9.22.8.Get Sub Set from TreeSet
9.22.9.Get Tail Set from TreeSet
9.22.10.Iterate through elements of TreeSet
9.22.11.Check if a particular value exists in TreeSet
9.22.12.Remove specified element from TreeSet
9.22.13.Remove all elements from TreeSet
9.22.14.The second two constructors are copy constructors
9.22.15.Sort items in a Set
9.22.16.To add a single element: the add() method: public boolean add(Object element)
9.22.17.Retrieving the Ends for a TreeSet
9.22.18.Fetching Elements: the iterator() method: public Iterator iterator()
9.22.19.Working with Subsets
9.22.20.The third method subSet() provides the end points: public SortedSet subSet(Object fromElement, Object toElement)
9.22.21.headset, tailset and subset
9.22.22.Viewing Subsets
9.22.23.Looping through a sorted set backwards