How to Replace a Element in Java ArrayList?

Last Updated : 08 Dec, 2020

To replace an element in Java ArrayList, set() method of java.util. ArrayList class can be used. The set() method takes two parameters-the indexes of the element which has to be replaced and the new element. The index of an ArrayList is zero-based. So, to replace the first element, 0 should be the index passed as a parameter.

Declaration:

public Object set(int index, Object element)

Return Value: The element which is at the specified index

Exception Throws: IndexOutOfBoundsException
when the index is out of range
i.e, index < 0 or index >= size()

Java

// Java program to demonstrate set()
// method of ArrayList
import java.io.*;
import java.util.*;
  
class GFG {
    public static void main(String[] args)
    {
        try {
            ArrayList<String> list = new ArrayList<>();
            // adding elements to the list
            list.add("A");
            list.add("B");
            list.add("C");
            list.add("D");
            System.out.println(list);
            // 2 is the index of the element "B".
            //"B" will be replaced by "E"
            list.set(2, "E");
            System.out.println(list);
            list.set(6, "z");
        }
        catch (Exception e) {
            System.out.println(e);
        }
    }
}

Output

[A, B, C, D]
[A, B, E, D]
java.lang.IndexOutOfBoundsException: Index 6 out of bounds for length 4

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