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: Boolean and it returns true if the object is added successfully.
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:
Program 1:
Java
// Java code to illustrate add(int index, E elements)import java.io.*;import java.util.*;public class ArrayListDemo { public static void main(String[] args) { // create an empty list with an initial // capacity List<String> list = new ArrayList<String>(5); // 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:
Java
// Java code to illustrate add(int index, E elements)import java.io.*;import java.util.*;public class ArrayListDemo { public static void main(String[] args) { // create an empty list with an initial capacity List<Integer> list = new ArrayList<Integer>(5); // use add() method to initially // add elements in the list list.add(10); list.add(20); list.add(30); // Add a new 25 at index 2 and print true if the element is added successfully System.out.println(list.add(2, 25)); // 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.
