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List lastIndexOf() Method in Java with Examples
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List indexOf() Method in Java with Examples

Last Updated : 29 Nov, 2024
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This method returns the index of the first occurrence of the specified element in this list, or -1 if this list does not contain the element.

Example:

Java 
// Java Program to Implement List // indexOf() Method import java.util.*;  class GFG  {     public static void main (String[] args)      {       	// List Created       	List<String> l = new ArrayList<String>();              	// Adding Elements       	l.add("Geeks");       	l.add("for Geeks");       	l.add("GFG");              	// Index Of        	System.out.println("Index of GFG is " + l.indexOf("GFG"));      	     } }

Output
Index of GFG is 2


Syntax of Method

public int indexOf(Object o)

Parameters: This function has a single parameter, i.e, the element to be searched in the list.

Returns: This method returns the index of first occurrence of the given element in the list and returns “-1” if element is not in the list.

Example of List indexOf() Method

Below programs show the implementation of this method.

Program 1:

Java 
// Java code to show the implementation of // indexOf method in list interface import java.util.*;  public class GfG  {     public static void main(String[] args)     {         // Initializing a list of type Linkedlist         List<Integer> l = new LinkedList<>();              	// Adding elements in List         l.add(1);         l.add(3);         l.add(5);         l.add(7);               System.out.println(l);              	// Index Of         System.out.println(l.indexOf(5));     } }

Output
[1, 3, 5, 7] 2

Program 2:

Below is the code to show implementation of list.hashCode() using Linkedlist.

Java 
// Java code to show the implementation of // indexOf method in list interface  import java.util.*;  public class GfG  {   	public static void main(String[] args)     {         // Initializing a list of type Linkedlist         List<String> l = new LinkedList<>();                	l.add("10");         l.add("15");         l.add("20");                System.out.println(l);         System.out.println(l.indexOf("20"));     } }

Output
[10, 15, 20] 2

Reference: Oracle Docs



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List lastIndexOf() Method in Java with Examples

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Article Tags :
  • Java
  • Java - util package
  • Java-Collections
  • Java-Functions
  • java-list
Practice Tags :
  • Java
  • Java-Collections

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