Open In App

Java ArrayList set() Method

Last Updated : 06 Aug, 2025
Comments
Improve
Suggest changes
13 Likes
Like
Report

The set() method of the ArrayList class in Java is used to replace an element at a specified position with a new value. This is very useful when we need to update an existing element in an ArrayList while maintaining the list's structure.

Example 1: Here, we will use the set() method to update an element in an ArrayList.

Java 
// Update an element in an ArrayList import java.util.ArrayList; public class GFG {  public static void main(String[] args) {    // Create an ArrayList and   // add elements  ArrayList<Integer> n = new ArrayList<>();  n.add(1);  n.add(2);  n.add(3);  n.add(4);  n.add(5);  // Print the original ArrayList  System.out.println("Before operation: " + n);  // Replace element at   // index 3 with 9  int r = n.set(3, 9);  System.out.println("After operation: " + n);  System.out.println("Replaced element: " + r);  } }

Output
Before operation: [1, 2, 3, 4, 5] After operation: [1, 2, 3, 9, 5] Replaced element: 4

Explanation: In the above example, it replaced an element in an ArrayList and prints both the updated list and the replaced element.

Syntax of ArrayList set() Method

public E set(int index, E element)

Parameters:

  • index: Index of the element to replace.
  • element: Element to be stored at the specified position.

Returns Value: It returns the element that was previously at the specified position.

Exception: IndexOutOfBoundsException: Thrown if the index is out of the valid range (index < 0 or index >= size).

Example 2: Here, this example will show how trying to replace an element at an invalid index results in an exception.

Java 
// Handling IndexOutOfBoundsException import java.util.ArrayList; public class GFG {  public static void main(String[] args) {  try {    // Create an ArrayList and add elements  ArrayList<Integer> n = new ArrayList<>();  n.add(1);  n.add(2);  n.add(3);  n.add(4);  n.add(5);  // Print the original ArrayList  System.out.println("Before operation: " + n);  // Attempt to replace an element at an invalid index  n.set(7, 9);  } catch (IndexOutOfBoundsException e) {    // Handle the exception  System.out.println("Exception: " + e);  }  } }

Output
Before operation: [1, 2, 3, 4, 5] Exception: java.lang.IndexOutOfBoundsException: Index 7 out of bounds for length 5

R

rohitprasad3
Improve
Article Tags :

Explore

Lightbox