Java Vector indexOf() Method

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Description

The indexOf(Object elem) method is used to search the first occurence of the given argument.The equality is tested by using the equals method.

Declaration

Following is the declaration for java.util.Vector.indexOf() method

public int indexOf(Object elem)

Parameters

elem − The input parameter is an object

Return Value

The return value is the index of the first occurrence of the argument in this vector.It returns -1 if the object is not found.

Exception

NA

Java Vector indexOf(Object elem,int index) Method

Description

This is another variant of previous indexOf() method.The only difference is that the search for the first occurence of the given argument starts at the index position mentioned as the second parameter.

Declaration

Following is the declaration for java.util.Vector.indexOf() method

public int indexOf(Object elem,int index)

Parameters

• elem − The input parameter is an object

• index − This is the non-negative index to start searching from

Return Value

The method call returns the index of the first occurrence of the object argument in this vector at position index or later in the vector.

Exception

IndexOutOfBoundsException − This exception is thrown if the index is negative

Getting Index of an Element of a Vector of Integer Example

The following example shows the usage of Java Vector indexOf(Object element) method to get the index of an element in this vector. We're adding couple of Integers to the Vector object using add() method calls per element and using indexOf(Object element) method, we're getting index of 3 and printing it.

package com.tutorialspoint;

import java.util.Vector;

public class VectorDemo {
   public static void main(String[] args) {

      // create an empty Vector vec with an initial capacity of 4      
      Vector<Integer> vec = new Vector<>(4);

      // use add() method to add elements in the vector
      vec.add(4);
      vec.add(3);
      vec.add(2);
      vec.add(3);

      // let us get the index of 3
      System.out.println("Index of 3 is: "+vec.indexOf(3));
   }   
}

Output

Let us compile and run the above program, this will produce the following result. Please note the index of first occurrence of 3 is 1 so 1 is printed instead of 3.

Index of 3 is: 1

Getting Index of an Element of a Vector of Integer Starting from Other Index Example

The following example shows the usage of Java Vector indexOf(Object element, Int index) method to get the index of an element in this vector starting from given index. We're adding couple of Integers to the Vector object using add() method calls per element and using indexOf() method, we're getting index of 3 and printing it.

package com.tutorialspoint;

import java.util.Vector;

public class VectorDemo {
   public static void main(String[] args) {

      // create an empty Vector vec with an initial capacity of 4      
      Vector<Integer> vec = new Vector<>(4);

      // use add() method to add elements in the vector
      vec.add(4);
      vec.add(3);
      vec.add(2);
      vec.add(3);
      vec.add(2);
      vec.add(3);

      /** let us get the index of 3
      * starting search from 2nd index
      */
      System.out.println("Index of 3 :"+vec.indexOf(3,2));
   }   
}

Output

Let us compile and run the above program, this will produce the following result.

Index of 3 :3

Getting Index of an Element of a Vector of String Example

The following example shows the usage of Java Vector indexOf(Object element) method to get the index of an element in this vector. We're adding couple of String to the Vector object using add() method calls per element and using indexOf(Object element) method, we're getting index of 3 and printing it.

package com.tutorialspoint;

import java.util.Vector;

public class VectorDemo {
   public static void main(String[] args) {

      // create an empty Vector vec with an initial capacity of 4      
      Vector<String> vec = new Vector<>(4);

      // use add() method to add elements in the vector
      vec.add("D");
      vec.add("C");
      vec.add("A");
      vec.add("C");

      // let us get the index of C
      System.out.println("Index of C is: "+vec.indexOf("C"));
   }   
}

Output

Let us compile and run the above program, this will produce the following result. Please note the index of first occurrence of C is 1 so 1 is printed instead of C.

Index of C is: 1