The indexOf() method of java.util.AbstractSequentialList class is used to return the index of the first occurrence of the specified element in this list, or -1 if this list does not contain the element. More formally, returns the lowest index i such that (o==null ? get(i)==null : o.equals(get(i))), or -1 if there is no such index.
Syntax:
public int indexOf(Object o)
Parameters: This method takes Object o as parameter which is the element to search for.
Return Value: This method returns the index of the first occurrence of the specified element in this list, or -1 if this list does not contain the element.
Exception: This method throws:
- ClassCastException: if the type of the specified element is incompatible with this list.
- NullPointerException: if the specified element is null and this list does not permit null elements.
Below are the examples to illustrate the indexOf() method.
Example 1:
// Java program to demonstrate indexOf()// method for AbstractSequentialList import java.util.*; public class GFG { public static void main(String[] args) { // Creating object of AbstractSequentialList AbstractSequentialList<Integer> arrlist1 = new LinkedList<Integer>(); // Populating arrlist1 arrlist1.add(10); arrlist1.add(20); arrlist1.add(30); arrlist1.add(40); arrlist1.add(50); // print arrlist1 System.out.println("AbstractSequentialList: " + arrlist1); // getting the index of element 30 // using indexOf() method int index = arrlist1.indexOf(30); // print the index System.out.println("Index of 30: " + index); }} |
Output:
AbstractSequentialList: [10, 20, 30, 40, 50] Index of 30: 2
Example 2:
// Java program to demonstrate indexOf()// method for AbstractSequentialList import java.util.*; public class GFG1 { public static void main(String[] args) { // Creating object of AbstractSequentialList AbstractSequentialList<Integer> arrlist1 = new LinkedList<Integer>(); // Populating arrlist1 arrlist1.add(10); arrlist1.add(20); arrlist1.add(30); arrlist1.add(40); arrlist1.add(50); // print arrlist1 System.out.println("LinkedListlist: " + arrlist1); // getting the index of element 100 // using indexOf() method int index = arrlist1.indexOf(null); // print the index System.out.println("Index of 100: " + index); }} |
Output:
LinkedListlist: [10, 20, 30, 40, 50] Index of 100: -1
