TreeSet headSet(E toElement boolean inclusive) method in java

Let’s learn TreeSet headSet(E toElement, boolean inclusive) method in java.

TreeSet headSet(E toElement, boolean inclusive) method in java

headSet(E toElement, boolean inclusive) method of TreeSet class returns a view of the portion of this set whose elements are less than(or equal to, if inclusive is true) toElement.

Syntax:

public NavigableSet<E> headSet(E toElement, boolean inclusive)

Parameters:

toElement high endpoint of the returned set.

inclusive true if the high endpoint is to be included in the returned view.

Throws:

ClassCastException – if toElement is not compatible with this set’s comparator.

NullPointerException – if toElement is null and this set uses natural ordering, or its comparator does not permit null elements.

IllegalArgumentException – if this set itself has are stricted range, and toElement lies outside the bounds of the range.

Now let’s see example on TreeSet headSet(E toElement, boolean inclusive) method.

import java.util.Iterator;
import java.util.TreeSet;
public class TreeSetHeadSetMethodExample
{
   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 for 5 inclusive true
      hs = (TreeSet)ts.headSet(5, true);
      // create iterator
      Iterator<Integer> iterate = hs.iterator();
      System.out.println("TreeSet data for '5' inclusive TRUE: ");
      while(iterate.hasNext())
      {
         System.out.println(iterate.next() + " ");
      }
      // get values for 5 inclusive false
      hs = (TreeSet)ts.headSet(5, false);
      iterate = hs.iterator();
      System.out.println("TreeSet data for '5' inclusive FALSE: ");
      while(iterate.hasNext())
      {
         System.out.println(iterate.next() + " ");
      }
   }
}

Output:

TreeSet data for ‘5’ inclusive TRUE:
1
2
3
4
5
TreeSet data for ‘5’ inclusive FALSE:
1
2
3
4