Check out example codes for "TreeSet headSet(E toElement) method in java". It will help you in understanding the concepts better.

Code Example 1

import java.util.Iterator;
import java.util.TreeSet;
public class TreeSetHeadSetEToElementMethodExample
{
   public static void main(String[] args)
   {
      TreeSet<Integer> ts = new TreeSet<Integer>();
      TreeSet<Integer> hs = new TreeSet<Integer>();
      ts.add(1);
      ts.add(2);
      ts.add(3);
      ts.add(4);
      ts.add(5);
      ts.add(6);
      // get values less than 5
      hs = (TreeSet)ts.headSet(5);
      // create iterator
      Iterator<Integer> iterate = hs.iterator();
      System.out.println("TreeSet data: ");
      while(iterate.hasNext())
      {
         System.out.println(iterate.next() + " ");
      }
   }
}

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