The pollFirst() method of NavigableSet interface in Java is used to retrieves and removes the first (lowest) element, or returns null if this set is empty.
Syntax:
E pollFirst()
Where, E is the type of elements maintained by this Set container.
Parameters: This function does not accepts any parameter.
Return Value: It returns returns null if this set is empty.
Below programs illustrate the pollFirst() method in Java:
Program 1: NavigableSet with integer elements.
// A Java program to demonstrate// pollFirst() method of NavigableSet import java.util.NavigableSet;import java.util.TreeSet; public class GFG { public static void main(String[] args) { NavigableSet<Integer> ns = new TreeSet<>(); ns.add(0); ns.add(1); ns.add(2); ns.add(3); ns.add(4); ns.add(5); ns.add(6); System.out.println("First lowest element removed is : " + ns.pollFirst()); }} |
Output:
First lowest element removed is : 0
Program 2: NavigableSet with string elements.
// A Java program to demonstrate// pollFirst() method of NavigableSet import java.util.NavigableSet;import java.util.TreeSet; public class GFG { public static void main(String[] args) { NavigableSet<String> ns = new TreeSet<>(); ns.add("A"); ns.add("B"); ns.add("C"); ns.add("D"); ns.add("E"); ns.add("F"); ns.add("G"); System.out.println("First lowest element removed is : " + ns.pollFirst()); }} |
Output:
First lowest element removed is : A
Reference: https://docs.oracle.com/javase/10/docs/api/java/util/NavigableSet.html#pollFirst(E)
