Java program converts ArrayList to array, array to ArrayList

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In this example, we will learn how to convert an ArrayList to an array and an array to an ArrayList in Java.

To understand this example, you should understand the followingJava programmingTopic:

• Java ArrayList class

• Java array

Example1Convert ArrayList to Array

import java.util.ArrayList;
class Main {
　　public static void main(String[] args) {
　　　　ArrayList<String> languages = new ArrayList<>();
　　　　//Add elements to the arraylist
　　　　languages.add("Java");
　　　　languages.add("Python");
　　　　languages.add("JavaScript");
　　　　System.out.println("ArrayList: "　+　languages);
　　　　//Create a new String type array
　　　　String[] arr = new String[languages.size()];
　　　　//Convert ArrayList to string array
　　　　languages.toArray(arr);
　　　　System.out.print("Array: ");
　　　　for(String item:arr) {
　　　　　　System.out.print(item+"	");
　　　　}
　　}
}

Output Result

ArrayList: [Java, Python, JavaScript]
Array: Java, Python, JavaScript,

In the above example, we created an ArrayList named languages. Note this line,

languages.toArray(arr);

In this case, the toArray() method converts the arraylist to an array and stores it in the string array arr.

NoteIf no parameters are passed to the toArray() method, it will return an array of type Object.

Example2Convert array to ArrayList

import java.util.Arrays;
import java.util.ArrayList;
class Main {
　　public static void main(String[] args) {
　　　　//Create an array
　　　　String[] array = {"Java", "Python", "C"};
　　　　System.out.println("Array: "　+　Arrays.toString(array));
　　　　//Convert an array to an arraylist
　　　　ArrayList<String> languages = new ArrayList<>(Arrays.asList(array));
　　　　System.out.println("ArrayList: "　+　languages);
　　}
}

Output Result

Array: [Java, Python, C]
ArrayList: [Java, Python, C]

In the above example, we created a String type array. Note the expression

Arrays.asList(array)

Here, the asList() method of the Arrays class converts the specified array to an arraylist.

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