TreeSet in Java

TreeSet provides an implementation of the Set interface that uses a tree for storage. Objects are stored in a sorted and ascending order. It contains only unique elements and the access & retrieval is quick.

Following is the list of the constructors supported by the TreeSet class.

Let us now see an example to work with TreeSet class −

Example

import java.util.*;
public class Main {
   public static void main(String args[]) {
      TreeSet ts = new TreeSet();
      // Add elements to the tree set
      ts.add("John");
      ts.add("Kevin");
      ts.add("Amy");
      ts.add("Ryan");
      ts.add("Katie");
      ts.add("Tom");
      System.out.println(ts);
   }
}

Output

[Amy, John, Katie, Kevin, Ryan, Tom]

Let us now see another example wherein we are checking for the existence of an element in the TreeSet −

Example

import java.util.*;
public class Main {
   public static void main(String args[]) {
      TreeSet ts = new TreeSet();
      // Add elements to the tree set
      ts.add("John");
      ts.add("Kevin");
      ts.add("Amy");
      ts.add("Ryan");
      ts.add("Katie");
      ts.add("Tom");
      Iterator<String> i = ts.iterator();
      while(i.hasNext()){
         System.out.println(i.next());
      }
      System.out.println("The Set has element 'Jacob'? = " +
      ts.contains("Jacob"));
      System.out.println("The Set has element 'Ryan'? = " +
      ts.contains("Ryan"));
   }
}

Output

Amy
John
Katie
Kevin
Ryan
Tom
The Set has element 'Jacob'? = false
The Set has element 'Ryan'? = true