Java ArrayList set() Method

Last Updated : 12 Dec, 2024

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

List equals() Method in Java with Examples

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