Java Program to Iterate over an ArrayList

May 26, 2023

What is ArrayList in Java ?

In Java, an ArrayList is a class that provides a resizable array implementation of the List interface. It allows you to store and manipulate a collection of objects in a dynamic manner, with the ability to add, remove, and access elements by their index.
Unlike a regular array, an ArrayList can grow and shrink in size dynamically as elements are added or removed. This makes it a more flexible data structure that can adapt to changing needs.

More on ArrayList in Java :

ArrayLists can be used to store objects of any type, including primitive data types like int, double, etc. To add elements to an ArrayList, you can use the add() method, and to retrieve an element, you can use the get() method. You can also remove elements using the remove() method and iterate over the elements using a for loop or an enhanced for loop.

Steps to Iterate over an ArrayList :

Create an ArrayList
Add elements to the ArrayList using the add() method
Get the size of the ArrayList using the size() method
Iterate over the elements in the ArrayList using a for loop:
a. Get the current element using the get() method
b. Do something with the current element
End the loop

Here’s a pseudo-code of the algorithm :

1. ArrayList myList = new ArrayList
2. myList.add("element1")
   myList.add("element2")
   myList.add("element3")
3. int size = myList.size()
4. for i = 0 to size - 1
     a. String currentElement = myList.get(i)
     b. // Do something with currentElement
5. end for

Explanation : In the above algorithm, we first create an ArrayList, add some elements to it, and then get the size of the ArrayList. We then use a for loop to iterate over the elements in the ArrayList.
Inside the loop, we get the current element using the get() method and then do something with it. This could be printing the element to the console, manipulating it in some way, or anything else that your program needs to do.
When the loop is complete, we have iterated over all elements in the ArrayList.

Example 1 :

Run

import java.util.ArrayList;

public class Main {
    public static void main(String[] args) {
        // Create a new ArrayList
        ArrayList< String> myList = new ArrayList<>();

        // Add some elements to the ArrayList
        myList.add("prepinsta");
        myList.add("prepinsta Prime");
        myList.add("coding");

        // Get the size of the ArrayList
        int size = myList.size();

        // Iterate over the elements in the ArrayList using a for loop
        for (int i = 0; i < size; i++) {
            String currentElement = myList.get(i);
            System.out.println(currentElement);
        }
    }
}

Output :

prepinsta
prepinsta Prime
coding

Explanation : In this example, we create a new ArrayList called myList and add three elements to it using the add() method. We then get the size of the ArrayList using the size() method, and iterate over the elements in the ArrayList using a for loop. Inside the loop, we get the current element using the get() method and then print it to the console using System.out.println(). When we run this program, it will output the following:

Example 2 :

Run

import java.util.ArrayList;

public class Main {
    public static void main(String[] args) {
        // Create a new ArrayList
        ArrayList< String> myList = new ArrayList<>();

        // Add some elements to the ArrayList
        myList.add("rishikesh");
        myList.add("ayush");
        myList.add("lakshit");

        // Iterate over the elements in the ArrayList using an enhanced for loop
        for (String currentElement : myList) {
            System.out.println(currentElement);
        }
    }
}

Output :

rishikesh
ayush
lakshit

Explanation : In this example, we create a new ArrayList called myList and add three elements to it using the add() method. We then use an enhanced for loop to iterate over the elements in the ArrayList.
Inside the loop, we declare a new variable called currentElement of type String, which represents the current element of the ArrayList. We then print the currentElement variable to the console using System.out.println().

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Java Program to Iterate over an ArrayList

What is ArrayList in Java ?

More on ArrayList in Java :

Steps to Iterate over an ArrayList :

Here’s a pseudo-code of the algorithm :

Example 1 :

Output :

Example 2 :

Output :

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