Sort items in a Java TreeSet

First, create a TreeSet and add elements to it −

TreeSet<String> set = new TreeSet<String>(); set.add("65"); set.add("45"); set.add("19"); set.add("27"); set.add("89"); set.add("57");

Now, sort it in ascending order, which is the default −

Iterator<String> i = set.iterator(); while(i.hasNext()){ System.out.println(i.next()); }

If you want to sort in descending order, then use the descendingIterator() method −

Iterator<String> j = set.descendingIterator(); while(j.hasNext()) { System.out.println(j.next()); }

The following is an example to sort items in a TreeSet in ascending and descending order −

Example

 Live Demo

import java.util.*; public class Demo { public static void main(String args[]){ TreeSet<String> set = new TreeSet<String>(); set.add("65"); set.add("45"); set.add("19"); set.add("27"); set.add("89"); set.add("57"); System.out.println("TreeSet elements (Sorted)..."); Iterator<String> i = set.iterator(); while(i.hasNext()) { System.out.println(i.next()); } System.out.println("\nTreeSet elements (Sorted) in Descending order..."); Iterator<String> j = set.descendingIterator(); while(j.hasNext()) { System.out.println(j.next()); } } }

Output

TreeSet elements (Sorted)... 19 27 45 57 65 89 TreeSet elements (Sorted) in Descending order... 89 65 57 45 27 19