Java ArrayList lastIndexOf() Method with Example

Java ArrayList lastIndexOf() Method with Example

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In the previous article we have discussed about Java ArrayList removeRange() Method with Example

In this article we are going to see the use of Java ArrayList lastIndexOf() method along with suitable examples.

Java ArrayList lastIndexOf() Method with Example

lastIndexOf():

This java.util.ArrayList.lastIndexOf() method is used to get the last index position of the specified element in the ArrayList.

It returns the last index position of the specified element (if exist) else returns -1.

Syntax:

arrayListName.lastIndexOf()

Where,

  • arrayListName refers to the name of your ArrayList.

Let’s see different examples to understand it more clearly.

Method-1: Java ArrayList lastIndexOf() Method – Example with String Type ArrayList

Approach:

  • Create a new ArrayList of type String.
  • Add string elements into the ArrayList using the add() method.
  • Display the ArrayList elements.
  • Then find the last index of the specified element using lastIndexOf() method.
  • Print the index position.

Program:

import java.util.*;
public class Main
{
    public static void main(String[] args)
    {
        // Create a ArrayList of string datatype
        ArrayList<String> arr = new ArrayList<String>();
        // Adding some elements to the ArrayList
        arr.add("book");
        arr.add("copy");
        arr.add("pen");
        arr.add("book");
        arr.add("pen");
        // Prints the ArrayList elements
        System.out.println("The elements of ArrayList are: "+arr);
        // get the position of Java occurred last
        System.out.println("Last Occurrence of book: " + arr.lastIndexOf("book"));
        System.out.println("Last Occurrence of notebook: " + arr.lastIndexOf("notebook"));
    }
}

Output:

The elements of ArrayList are: [book, copy, pen, book, pen]
Last Occurrence of book: 3
Last Occurrence of notebook: -1

Method-2: Java ArrayList lastIndexOf() Method – Example with Integer Type ArrayList

Approach:

  • Create a new ArrayList of type Integer.
  • Add Integer elements into the ArrayList using the add() method.
  • Display the ArrayList elements.
  • Then find the last index of the specified element using lastIndexOf() method
  • Print the index position.

Program:

import java.util.*;
public class Main
{
    public static void main(String[] args)
    {        
        // Create a ArrayList of string datatype
        ArrayList<Integer> arr = new ArrayList<Integer>();
        // Adding some elements to the ArrayList
        arr.add(2);
        arr.add(52);
        arr.add(13);
        arr.add(17);
        arr.add(1);
        arr.add(2);
        arr.add(52);
        arr.add(13);
        arr.add(17);
        // Prints the ArrayList elements
        System.out.println("The elements of ArrayList are: "+arr);
       // get the position of Java occurred last
       System.out.println("Last Occurrence of 2: " + arr.lastIndexOf(2));
       System.out.println("Last Occurrence of 99: " + arr.lastIndexOf(99));
    }
}

Output:

The elements of ArrayList are: [2, 52, 13, 17, 1, 2, 52, 13, 17]
Last Occurrence of 2: 5
Last Occurrence of 99: -1

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