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Java Vector indexOf() Method with Example

Vector Class indexOf() method: Here, we are going to learn about the indexOf() method of Vector Class with its syntax and example.
Submitted by Preeti Jain, on March 17, 2020

Vector Class indexOf() method

Syntax:

    public int indexOf(Object ob);
    public int indexOf(Object ob, int indices);

• indexOf() method is available in java.util package.
• indexOf(Object ob) method is used to return the index of the first occurrence of the given element.
• indexOf(Object ob, int indices) method is used to find the index of the first occurrence of the given object in this Vector and searching starts at the given indices.
• These methods may throw an exception at the time of returning an index.
  IndexOutOfBoundsException: This exception may throw when the given parameter is not in a range (indices<0).
• These are non-static methods and it is accessible with class objects and if we try to access these methods with the class name then we will get an error.

Parameter(s):

• In the first case, indexOf(Object ob),
  Object ob – represents the object for which index to be returned.
• In the first case, indexOf(Object ob, int indices),
  • Object ob – represents the index of searching starts.
  • int indices – represents the object for which index to be returned.

Return value:

In both the cases, the return type of the method is int,

• In the first case, it gets the index of the first occurrence of the given object when it exists otherwise it returns -1.
• In the second case, it returns the index of the first occurrence of the given object when exists.

Example:

// Java program to demonstrate the example 
// of indexOf() method of Vector

import java.util.*;

public class IndexOfVector {
    public static void main(String[] args) {
        // Instantiates a vector object     
        Vector < String > v = new Vector < String > (10);

        // By using add() method is to add
        // the elements in vector
        v.add("C");
        v.add("C++");
        v.add("SFDC");
        v.add("JAVA");
        v.add("C++");

        //Display Vector
        System.out.println("v: " + v);

        // By using indexOf(object) method is used
        // to return the index of first occurrence of the
        // given object

        System.out.println("v.indexOf(C++): " + v.indexOf("C++"));

        // By using indexOf(object, indices) method is used
        // to return the index of first occurrence of the
        // given object and searching starts from the 
        // given indices
        System.out.println("v.indexOf(C++,2): " + v.indexOf("C++", 2));
    }
}

Output

v: [C, C++, SFDC, JAVA, C++]
v.indexOf(C++): 1
v.indexOf(C++,2): 4