AbstractList indexOf() method in Java with Examples
The indexOf() method of java.util.AbstractList 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.
Below are the examples to illustrate the indexOf() method.
Example 1:
import java.util.*;
public class GFG1 {
public static void main(String[] argv)
throws Exception
{
try {
AbstractList<Integer>
arrlist1 = new ArrayList<Integer>();
arrlist1.add( 10 );
arrlist1.add( 20 );
arrlist1.add( 30 );
arrlist1.add( 40 );
arrlist1.add( 50 );
System.out.println( "ArrayListlist : "
+ arrlist1);
int index = arrlist1.indexOf( 30 );
System.out.println( "index : " + index);
}
catch (NullPointerException e) {
System.out.println( "Exception thrown : " + e);
}
}
}
|
Output:
ArrayListlist : [10, 20, 30, 40, 50]
index : 2
Example 2:
import java.util.*;
public class GFG1 {
public static void main(String[] argv)
throws Exception
{
try {
AbstractList<Integer>
arrlist1 = new ArrayList<Integer>();
arrlist1.add( 10 );
arrlist1.add( 20 );
arrlist1.add( 30 );
arrlist1.add( 40 );
arrlist1.add( 50 );
System.out.println( "ArrayListlist : "
+ arrlist1);
int index = arrlist1.indexOf( 25 );
System.out.println( "Index of 25 : "
+ index);
}
catch (NullPointerException e) {
System.out.println( "Exception thrown : " + e);
}
}
}
|
Output:
ArrayListlist : [10, 20, 30, 40, 50]
Index of 25 : -1
Example 3: For Null value
import java.util.*;
public class GFG1 {
public static void main(String[] argv) throws Exception
{
try {
AbstractList<Integer>
arrlist1 = new ArrayList<Integer>();
arrlist1.add( 10 );
arrlist1.add( 20 );
arrlist1.add( 30 );
arrlist1.add( 40 );
arrlist1.add( 50 );
System.out.println( "ArrayListlist : "
+ arrlist1);
Object value = null ;
int index = arrlist1.indexOf(value);
System.out.println( "Index of null : "
+ index);
}
catch (NullPointerException e) {
System.out.println( "Exception thrown : " + e);
}
}
}
|
Output:
ArrayListlist : [10, 20, 30, 40, 50]
Index of null : -1
Last Updated :
26 Nov, 2018
Like Article
Save Article
Share your thoughts in the comments
Please Login to comment...