Java LinkedList lastIndexOf() Method

The LinkedList.lastIndexOf() method in Java is used to find the index of the last occurrence of a specified element in the LinkedList. This guide will cover the method’s usage, explain how it works, and provide examples to demonstrate its functionality.

Table of Contents

1. Introduction
2. lastIndexOf Method Syntax
3. Examples
   • Finding the Last Index of an Element
   • Handling Non-Existent Elements
4. Conclusion

Introduction

The LinkedList.lastIndexOf() method is a member of the LinkedList class in Java. It allows you to find the index of the last occurrence of a specified element within the list. This method is particularly useful for locating elements and understanding their position in the list from the end.

lastIndexOf Method Syntax

The syntax for the lastIndexOf method is as follows:

public int lastIndexOf(Object o)

• o: The element to search for in the LinkedList.
• Returns: The index of the last occurrence of the specified element, or -1 if the element is not found.

Examples

Finding the Last Index of an Element

The lastIndexOf method can be used to find the index of the last occurrence of a specified element in a LinkedList.

Example

import java.util.LinkedList;

public class LastIndexOfExample {
    public static void main(String[] args) {
        // Creating a LinkedList of Strings
        LinkedList<String> list = new LinkedList<>();

        // Adding elements to the LinkedList
        list.add("Apple");
        list.add("Banana");
        list.add("Orange");
        list.add("Banana");

        // Finding the index of the last occurrence of "Banana"
        int lastIndex = list.lastIndexOf("Banana");

        // Printing the index
        System.out.println("Last index of 'Banana': " + lastIndex);
    }
}

Output:

Last index of 'Banana': 3

Handling Non-Existent Elements

If the specified element is not found in the LinkedList, the lastIndexOf method returns -1.

Example

import java.util.LinkedList;

public class LastIndexOfExample {
    public static void main(String[] args) {
        // Creating a LinkedList of Strings
        LinkedList<String> list = new LinkedList<>();

        // Adding elements to the LinkedList
        list.add("Apple");
        list.add("Banana");
        list.add("Orange");

        // Finding the index of a non-existent element "Grapes"
        int lastIndex = list.lastIndexOf("Grapes");

        // Printing the result
        System.out.println("Last index of 'Grapes': " + lastIndex);
    }
}

Output:

Last index of 'Grapes': -1

Conclusion

The LinkedList.lastIndexOf() method in Java provides a way to find the index of the last occurrence of a specified element in a LinkedList. By understanding how to use this method, you can efficiently locate elements and understand their position within your Java applications from the end of the list. Handling the potential return value of -1 ensures your code remains robust and can handle cases where the element is not found.