Java Vector indexOf() Method

The indexOf() Java Vector class method is used to get the index of the first occurrence of the specified element in the vector. There are two different types of Java indexOf() method which can be differentiated depending on its parameter. These are:

Java Vector indexOf(Object o) Method
Java Vector indexOf(Object o, int index) Method

indexOf(Object o) Method:

This method is used to get the index of the first occurrence of the specified element in the vector. If the element is not found, it returns -1.

indexOf(Object o, int index> c) Method:

This method is used to get the index of the first occurrence of the specified element in the vector. It starts searching for an element in the forward direction from the specified index. If the element is not found, it returns -1.

Syntax

Following is the declaration of indexOf() method:

public int indexOf(Object obj)
public int indexOf(Object obj, int index)

Parameter

Parameter	Description	Required/Optional
index	It is an index where to start searching for an element in the forward direction.	Required
obj	It is an element to search for.	Required

Return

The indexOf() method returns the index of the first occurrence of the specified element in this vector or returns -1 if the vector does not contain the element.

Exceptions

IndexOutOfBoundsException- This method has thrown an exception if the index of an array is out of range i.e. (index < 0 || index > size()).

Compatibility Version

Java 1.2 and above

Example 1

import java.util.*;
public class VectorIndexOfExample1 {  
	public static void main(String arg[]) {	
		//Create an empty Vector      
		Vector < Integer > in = new Vector < > ();
		//Add elements in the vector
		in.add(100);
		in.add(200);
		in.add(300);
		in.add(400);
            //Obtain an index of first occurrence of the specified element
		System.out.println("Index of element is: " +in.indexOf(300));
	      }            
}

Test it Now

Output:

Index of element is: 2

Example 2

import java.util.*;
public class VectorIndexOfExample2 {  
	public static void main(String arg[]) {	
		//Create a first empty vector   
	      Vector<String> vec = new Vector<>(4); 
	      //Add elements in the first vector	      
	      vec.add("Java");
	      vec.add("JavaScript");
	      vec.add("Android");
	      vec.add("Python");
            //Obtain an index of first occurrence of the specified element
		System.out.println("Index of element is: " +vec.indexOf("C"));
		System.out.println("The element is not found.");
	      }            
}

Test it Now

Output:

Index of element is: -1
The element is not found.

Example 3

import java.util.*;
public class VectorIndexOfExample3 {  
	public static void main(String arg[]) {	
		//Create a first empty vector   
	      Vector<String> vec = new Vector<>(4); 
	      //Add elements in the first vector	      
	      vec.add("Facebook");
	      vec.add("Whatsapp");
	      vec.add("Twitter");
	      vec.add("Instagram");
	      vec.add("Skype");
            //This would start searching of element from index -2
		System.out.println("Index of element is found at: " +vec.indexOf("Skype", -2));		
	}            
}

Test it Now

Output:

Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: -2
	at java.base/java.util.Vector.indexOf(Vector.java:430)
	at myPackage.VectorIndexOfExample3.main(VectorIndexOfExample3.java:14)

Example 4

import java.util.*;
public class VectorIndexOfExample4 {  
	public static void main(String arg[]) {	
		//Create an empty Vector      
		Vector < Integer > in = new Vector < > ();
		//Add elements in the vector
		in.add(101);
		in.add(201);
		in.add(301);
		in.add(401);
		in.add(501);
            //This would start searching of element from index 2
	      System.out.println("Index of element is found at: " +in.indexOf(401, 2));		
	}            
}

Test it Now

Output: