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.

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    // 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));
        }
    }

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    Output:

    The set contains: 
    13 31 45 72 89 
    Ceiling of 35: 45
    
    Ceiling of 100: null
    

    Program 2: To show NullPointerException in ceiling().

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    // 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);
            }
        }
    }

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    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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