Check if a List is empty in Java

This post will discuss how to check if a list is empty in Java.

1. Using `List.isEmpty()` method

A simple solution to check if a list is empty in Java is using the List’s isEmpty() method. It returns true if the list contains no elements. To avoid NullPointerException, precede the isEmpty method call with a null check.

import java.util.Collection;

import java.util.List;

class Main

{

public static boolean isEmpty(Collection<?> collection) {

return collection == null || collection.isEmpty();

}

public static void main(String[] args)

{

List<Integer> nums = List.of();

boolean isEmpty = isEmpty(nums);

if (isEmpty) {

System.out.println("The collection is empty");

} else {

System.out.println("The collection is not empty");

}

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Output:

The collection is empty

If you want to do the opposite, i.e., check if the list is not empty, you can use the following expression:

import java.util.List;

class Main

{

public static void main(String[] args)

{

List<Integer> nums = List.of();

boolean isNotEmpty = nums != null && !nums.isEmpty();

if (isNotEmpty) {

System.out.println("The collection is not empty");

} else {

System.out.println("The collection is empty");

}

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Output:

The collection is empty

2. Using Apache Commons Collections

To get a null-safe version of the isEmpty() method, you may want to use the CollectionUtils.isEmpty() method by Apache Commons Collections.

import org.apache.commons.collections4.CollectionUtils;

import java.util.List;

class Main

{

public static void main(String[] args)

{

List<Integer> nums = List.of();

boolean isEmpty = CollectionUtils.isEmpty(nums);

if (isEmpty) {

System.out.println("The collection is empty");

} else {

System.out.println("The collection is not empty");

}

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Output:

The collection is empty

3. Check empty or null in List of Lists

To check for an empty list or a null value in a List of Lists, you can use Stream API. For instance,

import java.util.Arrays;

import java.util.List;

class Main

{

public static boolean isAnyEmpty(List<List<Integer>> listOfLists) {

return listOfLists.stream()

.anyMatch(x -> x == null || x.isEmpty());

}

public static void main(String[] args)

{

List<List<Integer>> listOfLists = Arrays.asList(

List.of(1, 2, 3),

null,

List.of(4, 5)

);

boolean isAnyEmpty = isAnyEmpty(listOfLists);

if (isAnyEmpty) {

System.out.println("The collection is empty");

} else {

System.out.println("The collection is not empty");

}

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Output:

The collection is empty

Another alternative is to use the contains() method that checks for the specified value in the list. It can be used as follows:

import java.util.Arrays;

import java.util.Collections;

import java.util.List;

class Main

{

public static boolean isAnyEmpty(List<List<Integer>> listOfLists) {

return listOfLists.contains(null) || listOfLists.contains(Collections.emptyList());

}

public static void main(String[] args)

{

List<List<Integer>> listOfLists = Arrays.asList(

List.of(1, 2, 3),

List.of(),

List.of(4, 5)

);

boolean isAnyEmpty = isAnyEmpty(listOfLists);

if (isAnyEmpty) {

System.out.println("The collection is empty");

} else {

System.out.println("The collection is not empty");

}

Download Run Code

Output:

The collection is empty

That’s all about checking if a list is empty in Java.

Check if a List is empty in Java

1. Using List.isEmpty() method

2. Using Apache Commons Collections

3. Check empty or null in List of Lists

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1. Using `List.isEmpty()` method