The pollFirstEntry() method of NavigableMap interface in Java is used to remove and return a key-value mapping associated with the least key in this map, or null if the map is empty.
Syntax:
Map.Entry< K, V > pollFirstEntry()
Where, K is the type of key maintained by this map and V is the type of values mapped to the keys.
Parameters: This function does not accepts any parameter.
Return Value: It returns a key-value mapping associated with the least key after removing it from this map, or null if the map is empty.
Below programs illustrate the pollFirstEntry() method in Java:
Program 1: When the key is integer.
// Java code to demonstrate the working of// pollFirstEntry() method import java.io.*;import java.util.*; public class GFG { public static void main(String[] args) { // Declaring the NavigableMap of Integer and String NavigableMap<Integer, String> nmmp = new TreeMap<>(); // assigning the values in the NavigableMap // using put() nmmp.put(2, "two"); nmmp.put(7, "seven"); nmmp.put(3, "three"); System.out.println("First removed key-value from the map : " + nmmp.pollFirstEntry()); }} |
Output:
First removed key-value from the map : 2=two
Program 2: When the key is string.
// Java code to demonstrate the working of// pollFirstEntry() method import java.io.*;import java.util.*; public class GFG { public static void main(String[] args) { // Declaring the NavigableMap of Integer and String NavigableMap<String, String> tmmp = new TreeMap<>(); // assigning the values in the NavigableMap // using put() tmmp.put("one", "two"); tmmp.put("six", "seven"); tmmp.put("two", "three"); System.out.println("First removed key-value from the map : " + tmmp.pollFirstEntry()); }} |
Output:
First removed key-value from the map : one=two
Reference: https://docs.oracle.com/javase/10/docs/api/java/util/NavigableMap.html#pollFirstEntry()
