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AbstractSequentialList indexOf() method in Java with Example

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  • Last Updated : 24 Dec, 2018
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The indexOf() method of java.util.AbstractSequentialList class is used to return the index of the first occurrence of the specified element in this list, or -1 if this list does not contain the element. More formally, returns the lowest index i such that (o==null ? get(i)==null : o.equals(get(i))), or -1 if there is no such index.

Syntax:

public int indexOf(Object o)

Parameters: This method takes Object o as parameter which is the element to search for.

Return Value: 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.

Exception: This method throws:

  • ClassCastException: if the type of the specified element is incompatible with this list.
  • NullPointerException: if the specified element is null and this list does not permit null elements.

Below are the examples to illustrate the indexOf() method.

Example 1:




// Java program to demonstrate indexOf()
// method for AbstractSequentialList
  
import java.util.*;
  
public class GFG {
    public static void main(String[] args)
    {
  
        // Creating object of AbstractSequentialList
        AbstractSequentialList<Integer>
            arrlist1 = new LinkedList<Integer>();
  
        // Populating arrlist1
        arrlist1.add(10);
        arrlist1.add(20);
        arrlist1.add(30);
        arrlist1.add(40);
        arrlist1.add(50);
  
        // print arrlist1
        System.out.println("AbstractSequentialList: "
                           + arrlist1);
  
        // getting the index of element 30
        // using indexOf() method
        int index = arrlist1.indexOf(30);
  
        // print the index
        System.out.println("Index of 30: "
                           + index);
    }
}

Output:

AbstractSequentialList: [10, 20, 30, 40, 50]
Index of 30: 2

Example 2:




// Java program to demonstrate indexOf()
// method for AbstractSequentialList
  
import java.util.*;
  
public class GFG1 {
    public static void main(String[] args)
    {
        // Creating object of AbstractSequentialList
        AbstractSequentialList<Integer>
            arrlist1 = new LinkedList<Integer>();
  
        // Populating arrlist1
        arrlist1.add(10);
        arrlist1.add(20);
        arrlist1.add(30);
        arrlist1.add(40);
        arrlist1.add(50);
  
        // print arrlist1
        System.out.println("LinkedListlist: "
                           + arrlist1);
  
        // getting the index of element 100
        // using indexOf() method
        int index = arrlist1.indexOf(null);
  
        // print the index
        System.out.println("Index of 100: "
                           + index);
    }
}

Output:

LinkedListlist: [10, 20, 30, 40, 50]
Index of 100: -1

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