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);
}
} |
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);
}
} |
LinkedListlist: [10, 20, 30, 40, 50] Index of 100: -1