ConcurrentSkipListSet ceiling() method in Java

The java.util.concurrent.ConcurrentSkipListSet.ceiling() method is an in-built function in Java which returns the least element in this set greater than or equal to the given element, or null if there is no such element.

Syntax:

 ConcurrentSkipListSet.ceiling(E e)

Parameters: The function accepts a single parameter e i.e. the element to match.

Return Value: The function returns the least element greater than or equal to e, or null if there is no such element.

Exception: The function shows the following exceptions:

ClassCastException – if the specified element cannot be compared with the elements currently in the set

NullPointerException – if the specified element is null

Below programs illustrate the ConcurrentSkipListSet.ceiling() method:

Program 1: To find ceiling of a number.

// Java Program Demonstrate ceiling() 
// method of ConcurrentSkipListSet  
  
import java.util.concurrent.*; 
  
class ConcurrentSkipListSetCeilingExample1 { 
    public static void main(String[] args) 
    { 
        // Creating a set object 
        ConcurrentSkipListSet<Integer> Lset =  
                        new ConcurrentSkipListSet<Integer>(); 
  
        // Adding elements to this set 
        Lset.add(45); 
        Lset.add(72); 
        Lset.add(31); 
        Lset.add(13); 
        Lset.add(89); 
  
        // Printing elements of the set 
        System.out.println("The set contains: "); 
        for (Integer i : Lset) 
            System.out.print(i + " "); 
  
        // Ceiling of 35 
        System.out.println("\nCeiling of 35: " + Lset.ceiling(35)); 
  
        // Ceiling of 100 
        System.out.println("\nCeiling of 100: " + Lset.ceiling(100)); 
    } 
} 

Output:

The set contains: 
13 31 45 72 89 
Ceiling of 35: 45

Ceiling of 100: null

Program 2: To show NullPointerException in ceiling().

// Java Program Demonstrate ceiling() 
// method of ConcurrentSkipListSet 
  
import java.util.concurrent.*; 
import java.io.*; 
  
class ConcurrentSkipListSetCeilingExample2 { 
    public static void main(String[] args) throws IOException 
    { 
        // Creating a set object 
        ConcurrentSkipListSet<Integer> Lset =  
                            new ConcurrentSkipListSet<Integer>(); 
  
        // Adding elements to this set 
        Lset.add(45); 
        Lset.add(72); 
        Lset.add(31); 
        Lset.add(13); 
        Lset.add(89); 
  
        try { 
            // Ceiling of null 
            System.out.println("Ceiling of null: " + Lset.ceiling(null)); 
        } 
  
        catch (Exception e) { 
            System.out.println("Exception : " + e); 
        } 
    } 
} 

Output:

Exception : java.lang.NullPointerException

Reference : https://docs.oracle.com/javase/7/docs/api/java/util/concurrent/ConcurrentSkipListSet.html#ceiling(E)

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