What is the Comparator.nullsLast method in Java?

Overview

nullsLast is a static method of the Comparator interface that is used to return a Comparator that considers null elements to be greater than non-null elements.

The Comparator.nullsLast method takes a Comparator as a parameter, which is used to compare the non-null elements. If the passed comparator is null, then the non-null values are considered to be equal.

Given two inputs and a non-null Comparator as the parameter, the following scenarios are possible:

  • When both the inputs are null, the inputs are considered equal.
  • When both the inputs are non-null, the supplied Comparator is used for comparison.
  • When one of the inputs is null and the other is non-null, then the null input is considered to be greater than the non-null input.

The Comparator interface is defined in the java.util package. To import the Comparator interface, we use the following import statement:

import java.util.Comparator;

Syntax

public static <T> Comparator<T> nullsLast(Comparator<? super T> comparator)

Parameters

  • Comparator<? super T> comparator: The Comparator that is used to compare non-null values.

Return value

This method returns a Comparator.

Code

import java.util.Arrays;
import java.util.Comparator;
public class Main{
    public static void main(String[] args) {
        // Collection of strings
        String[] strings = {null, "hello", "educative", null, "edpresso"};
        // print the string collection
        System.out.println("Before sorting: " + Arrays.toString(strings));
        // Using the nullsLast method to sort the array
        Arrays.sort(strings, Comparator.nullsLast(Comparator.naturalOrder()));
        // print the sorted array
        System.out.println("After sorting: " + Arrays.toString(strings));
    }
}
Free AI Mock Interviews
Coding Interview
Coding PatternsFree Interview
Gain insights and practical experience with coding patterns through targeted MCQs and coding problems, designed to match and challenge your expertise level.
System Design
You TubeFree Interview
Learn to design a video streaming platform like YouTube by tackling functional and non-functional requirements, core components, and high-level to detailed design challenges.

Free Resources

License: Creative Commons-Attribution-ShareAlike 4.0 (CC-BY-SA 4.0)