Last Updated : 21 Sep, 2018
The
pollFirst()method of
java.util.concurrent.ConcurrentSkipListSetis an in-built function in Java which returns retrieves and removes the first (lowest) element, or returns null if this set is empty.
Syntax:public E pollFirst()Return Value:
The function returns retrieves and removes the first (lowest) element, or returns null if this set is empty. Below programs illustrate the ConcurrentSkipListSet.pollFirst() method:
Program 1: Java
// Java program to demonstrate pollFirst()
// method of ConcurrentSkipListSet
import java.util.concurrent.*;
class ConcurrentSkipListSetpollFirstExample1 {
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);
// Printing the content of the set
System.out.println("Contents of the set: " + Lset);
// Retrieving and removing first element of the set
System.out.println("The first element of the set: "
+ Lset.pollFirst());
// Printing the content of the set after pollFirst()
System.out.println("Contents of the set after pollFirst: "
+ Lset);
}
}
Output:
Contents of the set: [10, 20, 30, 40, 50] The first element of the set: 10 Contents of the set after pollFirst: [20, 30, 40, 50]Program 2: Java
// Java program to demonstrate pollFirst()
// method of ConcurrentSkipListSet
import java.util.concurrent.*;
class ConcurrentSkipListSetpollFirstExample2 {
public static void main(String[] args)
{
// Creating a set object
ConcurrentSkipListSet<Integer>
Lset = new ConcurrentSkipListSet<Integer>();
// Printing the content of the set
System.out.println("Contents of the set: " + Lset);
// Retrieving and removing first element of the set
System.out.println("The first element of the set: "
+ Lset.pollFirst());
}
}
Output:
Contents of the set: [] The first element of the set: nullReference: https://docs.oracle.com/javase/8/docs/api/java/util/concurrent/ConcurrentSkipListSet.html#pollFirst--
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