ConcurrentSkipListSet.floor(E e)

// Java program to demonstrate floor()
// method of ConcurrentSkipListSet
  
import java.util.concurrent.*;
  
class ConcurrentSkipListSetFloorExample1 {
    public static void main(String[] args)
    {
        // Creating a set object
        ConcurrentSkipListSet<Integer>
            Lset = new ConcurrentSkipListSet<Integer>();
  
        // Adding elements to this set
        for (int i = 10; i <= 50; i += 10)
            Lset.add(i);
  
        // Finding floor of 20 in the set
        System.out.println("The floor of 20 in the set "
                           + Lset.floor(20));
  
        // Finding floor of 39 in the set
        System.out.println("The floor of 39 in the set "
                           + Lset.floor(39));
  
        // Finding floor of 9 in the set
        System.out.println("The floor of 10 in the set "
                           + Lset.floor(9));
    }
}

The floor of 20 in the set 20
The floor of 39 in the set 30
The floor of 10 in the set null

// Java program to demonstrate floor()
// method of ConcurrentSkipListSet
  
import java.util.concurrent.*;
  
class ConcurrentSkipListSetFloorExample2 {
    public static void main(String[] args)
    {
        // Creating a set object
        ConcurrentSkipListSet<Integer>
            Lset = new ConcurrentSkipListSet<Integer>();
  
        // Adding elements to this set
        for (int i = 10; i <= 50; i += 10)
            Lset.add(i);
  
        // Trying to find the floor of null
        try {
            System.out.println("The floor of null in the set "
                               + Lset.floor(null));
        }
        catch (Exception e) {
            System.out.println("Exception: " + e);
        }
    }
}

Exception: java.lang.NullPointerException