Convert List to Array Java Example

Convert List to array Java example shows how to convert List to an array in Java including a primitive array using for loop, toArray method, Stream, and Apache Commons.

How to convert List to Array in Java?

The List can be converted to an array using the toArray method of the List.

1	<T> T[] toArray(T[] array)

This method returns an array containing all the elements of the argument list in the same sequence. The type of array returned from this method is the same as the argument array.

package com.javacodeexamples.basic.conversion;

import java.util.ArrayList;

import java.util.List;

public class ConvertListToArrayExample {

public static void main(String[] args) {

//create new List

List<String> listLanguages = new ArrayList<String>();

//Add elements to the List

listLanguages.add("Java");

listLanguages.add("C++");

listLanguages.add("C");

listLanguages.add("Cobol");

listLanguages.add("Fortran");

* To convert List to an array

* use toArray method of List

String[] strLanguages = listLanguages.toArray( new String[listLanguages.size()] );

for(String language : strLanguages)

System.out.println(language);

}

Output

Java

C++

Cobol

Fortran

Note:

If you pass an array smaller than the List to the toArray method, List will still be converted to an array of the correct type, but in that case, a new array will be created by JVM of the same type. It is always suggested to pass an array of the same size to avoid the creation of another array.

How to convert List to an array of primitive types?

The above method works only for the List containing object references. If you want to convert List to an array of primitive types, you need to loop through the elements of the List and fill the array as given in the below example. You can also use the Apache commons library.

a) Using For loop

package com.javacodeexamples.basic.conversion;

import java.util.ArrayList;

import java.util.List;

public class ConvertListToArrayExample {

public static void main(String[] args) {

List<Integer> listMarks = new ArrayList<Integer>();

listMarks.add(85);

listMarks.add(99);

listMarks.add(65);

listMarks.add(43);

listMarks.add(74);

//create new int array of same size

int[] marks = new int[listMarks.size()];

//loop through the list and fill int array

for(int i = 0; i < listMarks.size(); i++)

marks[i] = listMarks.get(i);

//print array

System.out.println("Convert List to primitive array");

for(int mark : marks)

System.out.println(mark);

}

Output

Convert List to primitive array

b) Using Apache Commons library

You can use the toPrimitive method of the ArrayUtils class of the Apache commons library as given below.

List<Integer> listMarks = new ArrayList<Integer>();

listMarks.add(85);

listMarks.add(99);

listMarks.add(65);

listMarks.add(43);

listMarks.add(74);

//convert Integer[] to int[]

int[] marks = ArrayUtils.toPrimitive( listMarks.toArray( new Integer[listMarks.size()]) );

//print array

System.out.println("Convert List to primitive array");

for(int mark : marks)

System.out.println(mark);

Output

Convert List to primitive array

How to convert using the Java 8 Stream?

//create new List

List<String> listLanguages = new ArrayList<String>();

//Add elements to the List

listLanguages.add("Java");

listLanguages.add("C++");

listLanguages.add("C");

listLanguages.add("Cobol");

listLanguages.add("Fortran");

//use Java 8 Stream to convert List to array

String[] strLanguages = listLanguages.stream().toArray(String[]::new);

//print array

for(String language : strLanguages)

System.out.println(language);

Output

Java

C++

Cobol

Fortran

This example is a part of the Java Array tutorial and Java ArrayList tutorial.

Please let me know your views in the comments section below.

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Rahim

I have a master's degree in computer science and over 18 years of experience designing and developing Java applications. I have worked with many fortune 500 companies as an eCommerce Architect. Follow me on LinkedIn and Facebook.