How to use Arraylist in Java

In this example, we will see how to use ArrayList in Java. ArrayList implements List interface, java.util.ArrayList class is re-sizable which will let you add or remove elements from it with ease. This makes the ArrayList have an upper hand over the Java arrays, as arrays use static data structure and we need to specify the size of the array which cannot be changed.

import java.util.ArrayList;

public class ArrayListExample {

	public static void main(String args[]) 
	{
		// Creating an empty array list
		ArrayList al = new ArrayList();
		
		//Adding elements to the arraylist
		al.add("Element1");
		al.add("Element2");
		al.add("Element3");

		//Get the index of a particular element
		System.out.println("Index of Element2 is >>>"+al.indexOf("Element2"));
		
		//Check if the list has a particular element
		//contains() method returns true if the element is present
		System.out.println("Does Element3 present in this list ??? "+al.contains("Element3"));
		
		//Check if the list has elements in it or not
		//isEmpty() method returns true when there is no element in the list
		System.out.println("Is this list empty??? "+al.isEmpty());
		
		//Get the size of the list
		System.out.println("The size of the list is >>>"+al.size());
		
		//inserting a element into the list with index
		/*Adding based on position will try to insert element in that specified index, 
		 * if an element is already present, the existing element will be pushed to the next index.
		 */
		al.add(1,"Element1-1");
		//List after adding a new element
		System.out.println("List after adding a new element"+al);
		
		//Retrieve an element at the particualr index
		//get() method will return the object which is present at the particular index
		System.out.println("Element present at index 1 is >>>"+al.get(1));
		
		//Removing a element from the list using index
		//remove() method will help us removing the element which is present at that index
		al.remove(1);
		//List after removing a element
		System.out.println("List after removing a element"+al);
		
		//Removing the first occurance of a element
		//This way we can remove the first occurance of the element "Element2"
		al.remove("Element2");
		//List after removing a element
		System.out.println("List after removing a element"+al);
		
		//inserting a element into the list with index
		/*set() method will replace the element which is present at the particular index
		 */
		al.set(1,"Element1-1");
		//List after setting a new element 
		System.out.println("List after setting a new element"+al);
	}
}

Output

Index of Element2 is >>>1
Does Element3 present in this list ??? true
Is this list empty??? false
The size of the list is >>>3
List after adding a new element[Element1, Element1-1, Element2, Element3]
Element present at index 1 is >>>Element1-1
List after removing a element[Element1, Element2, Element3]
List after removing a element[Element1, Element3]
List after setting a new element[Element1, Element1-1]