LinkedList indexOf() Method in Java

LinkedList indexOf() Method in Java

Last Updated : 18 Dec, 2024

In Java, the indexOf() method of the LinkedList class is used to find the index of the first occurrence of the specified element in the list.

Syntax of LinkedList indexOf() Method

public int indexOf(Object o);

Parameter: This method takes an object "o" as an argument.

Return type:

It returns the index of the first occurrence of the specified element.
If the element is not present, it will return -1.

Example: Here, we use the indexOf() method to find the index of the specified element in the list.

Java

// Java Program to Demonstrate the 
// use of indexOf() in the LinkedList
import java.util.LinkedList;

public class Geeks {
    public static void main(String args[]) {
      
        // Create an empty list
        LinkedList<Integer> l = new LinkedList<>();

        // Use add() method to add 
        // elements in the list
        l.add(10);
        l.add(20);
        l.add(30);
        l.add(40);
        l.add(50);

        System.out.println("The LinkedList is: " + l);

        // Use indexOf() to return 
        // the index of an element
        System.out.println(
            "The first occurrence of 20 is at index:"
            + l.indexOf(20));
        System.out.println(
            "The first occurrence of 90 is at index: "
            + l.indexOf(90));
    }
}

Output

The LinkedList is: [10, 20, 30, 40, 50]
The first occurrence of 20 is at index:1
The first occurrence of 90 is at index: -1

Points to Remember:

The index returned is zero-based, meaning the first element has an index of 0.
If the list contains duplicate elements, indexOf() returns the index of the first occurrence.
If the specified element is null, the method can handle it if the list allows null elements.

LinkedList indexOf() Method in Java

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