Java ArrayList

The ArrayList class in Java is a resizable array that implements the List interface. It provides methods for adding, removing, and accessing elements in the list, as well as methods for searching, sorting, and iterating over the elements of the list.

Here is an example of how to create an ArrayList and add elements to it:

import java.util.ArrayList;

public class ArrayListExample {

    public static void main(String[] args) {
        ArrayList<String> words = new ArrayList<>();
        words.add("hello");
        words.add("world");
        words.add("goodbye");
        words.add("moon");
    }
}

This code creates an ArrayList of strings called words and adds the elements "hello", "world", "goodbye", and "moon" to the list using the add() method.

You can also create an ArrayList from an existing collection using the ArrayList(Collection<? extends E> c) constructor. For example:

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

...

List<String> list = Arrays.asList("hello", "world", "goodbye", "moon");
ArrayList<String> words = new ArrayList<>(list);

This code creates a List of strings using the asList() method of the Arrays class and assigns it to the list variable. It then creates an ArrayList of strings called words and initializes it with the elements of the listList.

To access the elements of an ArrayList, you can use the get() method, which takes an index as an argument and returns the element at that index. For example:

String first = words.get(0);
String second = words.get(1);

This code gets the elements at index 0 and 1 in the words list and assigns them to the first and second variables, respectively.

You can also use the set() method to replace an element in the list .