The add(int index, E ele) method of List interface in Java is used to insert the specified element at the given index in the current list. Syntax:
public add(int index, E element)
Parameter: This method accepts two parameters as shown in the above syntax:
- index: This parameter specifies the index at which we the given element is to be inserted.
- element: This parameter specifies the element to insert in the list.
Return Value: Â Boolean and it returns true if the object is added successfully.Â
Exceptions:
- UnsupportedOperationException – It throws this exception if the add() operation is not supported by this list.
- ClassCastException – It throws this exception if the class of the specified element prevents it from being added to this list.
- NullPointerException – It throws this exception if the specified element is null and this list does not permit null elements.
- IllegalArgumentException – It throws this exception if some property of this element prevents it from being added to this list.
Below programs illustrate the List.add(int index, E element) method:Â
Program 1:Â
Java
// Java code to illustrate add(int index, E elements)Â
import java.io.*;import java.util.*;Â
public class ArrayListDemo {    public static void main(String[] args)    {        // create an empty list with an initial        // capacity        List<String> list = new ArrayList<String>(5);Â
        // use add() method to initially        // add elements in the list        list.add("Geeks");        list.add("For");        list.add("Geeks");               // Add a new element at index 0        list.add(0, "Hello");               // prints all the elements available in list        for (String str : list) {            System.out.print(str + " ");        }    }} |
Output
Hello Geeks For Geeks
Program 2:Â
Java
// Java code to illustrate add(int index, E elements)import java.io.*;import java.util.*;Â
public class ArrayListDemo {Â Â Â Â public static void main(String[] args)Â Â Â Â {Â
        // create an empty list with an initial capacity        List<Integer> list = new ArrayList<Integer>(5);Â
        // use add() method to initially        // add elements in the list        list.add(10);        list.add(20);        list.add(30);Â
        // Add a new 25 at index 2 and print true if the element is added successfully        System.out.println(list.add(2, 25));Â
        // prints all the elements available in list        for (Integer num : list) {            System.out.print(num + " ");        }    }} |
Output:
10 20 25 30
The Time Complexity of add( E element)) is O(1).
The Time Complexity of add(int index, E element)) is O(n) i.e linear.
