The java.util.TreeSet.add() method

The method add(Object o) is used to add an element to the TreeSet if it does not exist in the list.

Here's how to declare the java.util.TreeSet.add():

public boolean add(Object o): This method returns true if the TreeSet does not contain this element and is inserted successfully.

Example

The following example shows the use of the java.util.TreeSet.add():  

import java.util.Iterator; 
import java.util.TreeSet; 

public class Treeset {
 public static void main(String[] args) {
 // creating a TreeSet
 TreeSet treeadd = new TreeSet(); 
 
 // add values to TreeSet
 treeadd.add(54); 
 treeadd.add(40); 
 treeadd.add(96); 
 treeadd.add(15); 
 treeadd.add(34); 
 
 // create an iterator to browse TreeSet
 Iterator iterator = treeadd.iterator(); 
 
 // display all TreeSet elements
 System.out.println("TreeSet elements"); 
 while (iterator.hasNext()){
 System.out.println(iterator.next()); 
 }
 } 
}
Let's compile and run the above program, this will produce the following result: 

TreeSet15
34
40
54
96