Java Utility Library

Java TreeMap - pollFirstEntry() Method

The java.util.TreeMap.pollFirstEntry() method 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

public Map.Entry<K,V> pollFirstEntry()

Here, K and V are the type of key and value respectively maintained by the container.

Parameters

No parameter is required.

Return Value

Returns the removed first entry of this map, or null if this map is empty.

Exception

NA.

Example:

In the example below, the java.util.TreeMap.pollFirstEntry() method is used to remove the key-value mapping associated with the least key in the given map.

import java.util.*;

public class MyClass {
  public static void main(String[] args) {
    //creating a treemap
    TreeMap<Integer, String> MyMap = new TreeMap<Integer, String>();

    //populating the map
    MyMap.put(102, "John");
    MyMap.put(103, "Marry");
    MyMap.put(101, "Kim");
    MyMap.put(104, "Jo");
    MyMap.put(105, "Sam");

    //printing the map
    System.out.println("MyMap contains: " + MyMap); 

    //removing the first entry from the map
    MyMap.pollFirstEntry(); 

    //printing the map
    System.out.println("MyMap contains: " + MyMap);         
  }
}

The output of the above code will be:

MyMap contains: {101=Kim, 102=John, 103=Marry, 104=Jo, 105=Sam}
MyMap contains: {102=John, 103=Marry, 104=Jo, 105=Sam}

❮ Java.util - TreeMap