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:
// 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());    }} |
Output:
The lowest element in the set: 10
Program 2: Program to show NoSuchElementException in first().
// 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);        }    }} |
Output:
Exception :java.util.NoSuchElementException
Reference: https://docs.oracle.com/javase/8/docs/api/java/util/concurrent/ConcurrentSkipListSet.html#first–
