Java convert List to Array

In this post, we will see how to convert List to Array in java.

There are many ways to convert List to Array in java
[toc]

Using toArray() method

We can use toArray() method to convert List to String. We can either pass a array of size as List’s length or we can pass empty array.
This returns an array containing all the elements of the list in correct order.
There two overloaded methods for toArray().
Syntax:

T[] toArray(T[] x)
and
public Object[] toArray();

Where,T represents generic.

Example:

import java.util.List;
import java.util.ArrayList;

class ListToArrayToArray
{
    public static void main(String arg[])
    {
        //creation of list of type String
        List<String> list=new ArrayList<>();
        list.add("Hello");
        list.add("I");
        list.add("Am");
        list.add("John");
        //print content of list
        System.out.println("Elements of list are:");
        System.out.println(list);
        //create an String array of size of list
        //list.size() to know size of list
        String[] arr=new String[list.size()];
        //assign all the element of list in array using toArray() method by passing array
        arr=list.toArray(arr);
        System.out.println("Elements of Array are:");
        for(int i=0; i < arr.length; i++)  
        {
            //printing element of array
            System.out.println(arr[i]);
        }
        // print elements of array using for each loop
        System.out.println("Display using for each loop:");
        for (String a: arr)
        {
            System.out.println(a);
        }
    }
}

OUTPUT:

Please note that if you do not pass any parameter to toArray() method, it will give us Object array.

Using Java 8’s Stream

We can simply use java 8‘ stream’s toArray() method to convert List to array.

package org.arpit.java2blog;

import java.util.ArrayList;
import java.util.List;

public class ListToArrayJava8Main {
    public static void main(String[] args) {
        //creation of list of type String
        List<String> list=new ArrayList<>();
        list.add("John");
        list.add("Martin");
        list.add("Mary");
        list.add("Andrew");
        //print content of list
        System.out.println("Elements of list are:");
        System.out.println(list);

        String[] arr=list.stream().toArray(String[]::new);

        System.out.println("Elements of Array are:");
        for(int i=0; i < arr.length; i++)  
        {
            //printing element of array
            System.out.println(arr[i]);
        }
    }
}

Output:

Using Arrays.copyOf

We can use Arrays.copyOf() method also to convert List to Array. We need to use toArray() method and pass it to Arrays.copyOf() method to convert it to specified type

package org.arpit.java2blog;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

public class ListToArrayCopyOfMain {
    public static void main(String[] args) {
        //creation of list of type String
        List<String> list=new ArrayList<>();
        list.add("John");
        list.add("Martin");
        list.add("Mary");
        list.add("Andrew");
        //print content of list
        System.out.println("Elements of list are:");
        System.out.println(list);

        String[] arr=Arrays.copyOf(list.toArray(),list.size(),String[].class);

        System.out.println("Elements of Array are:");
        for(int i=0; i < arr.length; i++)  
        {
            //printing element of array
            System.out.println(arr[i]);
        }
    }
}

Output:

Using System.arraycopy

We can use System.arraycopy() method which copies an specified array, starting at the specified position, to the specified position of the target array.

package org.arpit.java2blog;

import java.util.ArrayList;
import java.util.List;

public class ListToArrayArrayCopyMain {
    public static void main(String[] args) {
        //creation of list of type String
        List<String> list=new ArrayList<>();
        list.add("India");
        list.add("China");
        list.add("Nepal");
        list.add("Bhutan");
        //print content of list
        System.out.println("Elements of list are:");
        System.out.println(list);
        //create an String array of size of list
        //list.size() to know size of list
        String[] arr=new String[list.size()];
        System.arraycopy(list.toArray(), 0, arr, 0, list.size());

        System.out.println("Elements of Array are:");
        for(int i=0; i < arr.length; i++)  
        {
            //printing element of array
            System.out.println(arr[i]);
        }
    }
}

Output:

Manual method

This method use loop and run it until the size of list and one by one get elements from list and add it to Array.

Example:

package org.arpit.java2blog;

import java.util.List;
import java.util.ArrayList;
public class ListToArrayManualMain
{
    public static void main(String arg[])
    {
        //create and initialization of list
        List<Integer> list=new ArrayList<>();
        list.add(800);
        list.add(600);
        list.add(400);
        list.add(200);
        //print content of list
        System.out.print("Elements of list are:");
        System.out.println(list);
        //create an integer array of size of list
        //list.size() to know size of list
        int[] ar=new int[list.size()];
        System.out.println("Elements of Array are:");
        //assigning of element of list one by one to array ar
        for(int i=0;  i < list.size();  i++)
        {
            ar[i]=list.get(i);
            //printing element of array
            System.out.println(ar[i]);
        }
    }
}

OUTPUT:

That’s all about converting List to Array in java.