The indexOf() method of AbstractList class in Java

The indexOf() method is used to return the index of the first occurrence of the specified element in this list. If the list is empty, it returns -1.

The syntax is as follows.

int indexOf(Object ob)

Here, the parameter ob is the element to search for.

To work with the AbstractList class, import the following package.

import java.util.AbstractList;

The following is an example to implement indexOf() method of the AbstractlList class in Java.

Example

 Live Demo

import java.util.ArrayList;
import java.util.AbstractList;
public class Demo {
   public static void main(String[] args) {
      AbstractList<Integer> myList = new ArrayList<Integer>();
      myList.add(5);
      myList.add(20);
      myList.add(35);
      myList.add(47);
      myList.add(55);
      myList.add(70);
      myList.add(100);
      myList.add(140);
      myList.add(100);
      myList.add(250);
      System.out.println("Elements in AbstractList = " + myList);
      System.out.println("Last Index of the element 100 = " + myList.lastIndexOf(100));
   }
}

Output

Elements in AbstractList = [5, 20, 35, 47, 55, 70, 100, 140, 100, 250]
Last Index of the element 100 = 8