Java -TreeSet class

• TreeSet contains unique elements only like HashSet. The TreeSet class implements .NavigableSet interface that extends the SortedSet interface.
• TreeSet sorts the elements in the ascending order.
• TreeSet allows null element.
• TreeSet class is  not synchronized.
• it can be synchronized explicitly like this: SortedSet s = Collections.synchronizedSortedSet(new TreeSet(...));

 

class TreeSet <T>

We can create TreeSet for storing String type elements as follows:

TreeSet <String> hs=new TreeSet <String> ();

We can create TreeSet for storing Integer type elements as follows:

TreeSet <Integer> hs=new TreeSet <Integer> ();

TreeSet Example:

1. import java.util.*;
2. class TreeSetDemo
   {
3.  public static void main(String args[]){
5.   TreeSet<String> ts=new TreeSet<String>();
6.   ts.add(“C”);
7.   ts.add(“B”);
8.   ts.add(“D”);
9.   ts.add(“A”);
11.   Iterator<String> itr=ts.iterator();
12.   while(itr.hasNext()){
13.    System.out.println(itr.next());
14.   }
15.  }
16. }

Output:
       A
       B
       C
       D

Another TreeSet Example:

import java.util.TreeSet;
public class TreeSetDemo1 {
     public static void main(String args[]) {
         // TreeSet declaration of String Type
         TreeSet<String> ts = new TreeSet<String>();

         // Adding elements to TreeSet of type String
         ts.add("ABC");
         ts.add("String");
         ts.add("School");
         ts.add("Pen");
         ts.add("Ink");
         ts.add("Book");

         //Displaying element of TreeSet
         System.out.println(ts);

         // TreeSet of Integer Type
         TreeSet<Integer> ts2 = new TreeSet<Integer>();

         // Adding elements to TreeSet of type <Integer>
         ts2.add(80);
         ts2.add(70);
         ts2.add(10);
         ts2.add(0);
         ts2.add(30);
         ts2.add(22);
         System.out.println(ts2);
    }
 }
output

[ABC, Book, Ink, Pen, School, String]
[0, 10, 22, 30, 70, 80]