Java ArrayList lastIndexOf() Method

December 9, 2022

What is ArrayList ?

ArrayList provides us with dynamic arrays. The ArrayLists are resizable in nature , we can add or remove an element at anytime. It is not compulsory to mention size while declaring it. The ArrayList is a part of Java framework and can be found in the java.util pacakge. ArrayList have many inbuilt methods which we can use. One of them is Java ArrayList lastIndexOf() Method.

Here on this page we will discuss about ArrayList lastIndexOf() method.

Java ArrayList lastIndexOf() Method

The lastIndexOf() method can be found in java.util.ArrayList package. This method is used to find the last occurrence of the element in the arraylist. If the element is not present in the list it return -1. It’s syntax, parameters, return values are discussed below with examples.

Syntax :

ArrayList.lastIndexOf(object);

Parameters :

ArrayList: name of the list.
object: the element whose last index is to be returned.

lastIndexOf() return values :

1. Return the last index of the element if it is present in the list.
2. Return -1 if the element is not present in the list.

Polymorphism in Java

Encapsulation in Java

Abstraction in Java

Multithreading in Java

ArrayList lastIndexOf() Method Examples:

Example :

Run

import java.util.ArrayList;

class Main
{
  public static void main (String[]args)
  {
    // creating an String ArrayList
    ArrayList < Integer > list = new ArrayList <> ();

    // adding elements to the list
    list.add (1);
    list.add (4);
    list.add (3);
    list.add (4);
    list.add (8);
    list.add (4);
    list.add (9);

    // check the last index of 4
    int result = list.lastIndexOf (4);

      System.out.println ("Last index of 4 is " + result);

    // check the last index of 7
      result = list.lastIndexOf (7);

      System.out.println ("Last index of 7 is " + result);
  }
}

Output :

Last index of 4 is : 5
Last index of 7 is : -1

What happened above When the lastIndexOf() Method is called first time , it checks for the last occurrence of '4' since its last occurrence is at position 5 the method returns 5, but when the method is called second time , it checks for the last occurrence of 7 since, 7 is not present in the list it retuns -1.

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Java ArrayList lastIndexOf() Method

What is ArrayList ?

Java ArrayList lastIndexOf() Method

Syntax :

Parameters :

lastIndexOf() return values :

ArrayList lastIndexOf() Method Examples:

Example :

Output :

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