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 a upper hand over the Java arrays, as arrays uses 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]