ConcurrentSkipListSet first() method in Java

The first() method of java.util.concurrent.ConcurrentSkipListSet is an in-built function in Java which returns the first (lowest) element currently in this set.

Syntax:

ConcurrentSkipListSet.first()

Return Value: The function returns the first (lowest) element currently in this set.



Exception: The function throws NoSuchElementException if this set is empty.

Below programs illustrate the ConcurrentSkipListSet.first() method:

Program 1:

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// Java Program Demonstrate first()
// method of ConcurrentSkipListSet
  
import java.util.concurrent.ConcurrentSkipListSet;
  
class ConcurrentSkipListSetFirstExample1 {
    public static void main(String[] args)
    {
  
        // Initializing the set
        ConcurrentSkipListSet<Integer>
            set = new ConcurrentSkipListSet<Integer>();
  
        // Adding elements to first set
        set.add(10);
        set.add(35);
        set.add(20);
        set.add(25);
  
        System.out.println("The lowest element in the set: "
                                              + set.first());
    }
}

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Output:

The lowest element in the set: 10


Program 2:
Program to show NoSuchElementException in first().

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// Java Program Demonstrate first()
// method of ConcurrentSkipListSet
  
import java.util.concurrent.ConcurrentSkipListSet;
  
class ConcurrentSkipListSetFirstExample2 {
    public static void main(String[] args) throws InterruptedException
    {
  
        // Initializing the set
        ConcurrentSkipListSet<Integer>
            set = new ConcurrentSkipListSet<Integer>();
        try {
            System.out.println("The lowest element in the set: " +
                                                       set.first());
        }
        catch (Exception e) {
            System.out.println("Exception :" + e);
        }
    }
}

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Output:

Exception :java.util.NoSuchElementException

Reference: https://docs.oracle.com/javase/8/docs/api/java/util/concurrent/ConcurrentSkipListSet.html#first–



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