CopyOnWriteArrayList indexOf() method in Java
Last Updated :
31 May, 2023
The indexOf(Object o) method of CopyOnWriteArrayList returns the first occurrence of the element passed in the list. It returns -1 if the element is not present in the list.
Syntax:
public int indexOf(Object o)
Parameters: The function accepts a parameter o whose first occurrence is to be returned.
Return Value: The function returns the first occurrence of the element. It returns -1 if the element is not present in the list.
Below programs illustrate the above function:
Program 1:
Java
// Java Program to illustrate the CopyOnWriteArrayList
// indexOf() method in Java
import java.util.concurrent.CopyOnWriteArrayList;
import java.util.*;
public class GFG {
public static void main(String[] args)
{
// create object of CopyOnWriteArrayList
CopyOnWriteArrayList<Integer> ArrLis
= new CopyOnWriteArrayList<Integer>();
// Add elements
ArrLis.add(32);
ArrLis.add(67);
ArrLis.add(67);
ArrLis.add(100);
// print CopyOnWriteArrayList
System.out.println("CopyOnWriteArrayList: " + ArrLis);
// first occurrence of 67
System.out.println("indexOf value: " + ArrLis.indexOf(67));
}
}
Output:CopyOnWriteArrayList: [32, 67, 67, 100]
indexOf value: 1
Program 2:
Java
// Java Program to illustrate the CopyOnWriteArrayList
// indexOf() method in Java
import java.util.concurrent.CopyOnWriteArrayList;
import java.util.*;
public class GFG {
public static void main(String[] args)
{
// create object of CopyOnWriteArrayList
CopyOnWriteArrayList<Integer> ArrLis
= new CopyOnWriteArrayList<Integer>();
// Add elements
ArrLis.add(32);
ArrLis.add(67);
ArrLis.add(67);
ArrLis.add(100);
// print CopyOnWriteArrayList
System.out.println("CopyOnWriteArrayList: "
+ ArrLis);
// 200 is not present
System.out.println("indexOf value: "
+ ArrLis.indexOf(200));
}
}
Output:CopyOnWriteArrayList: [32, 67, 67, 100]
indexOf value: -1
The indexOf(E e, int index) method of CopyOnWriteArrayList returns the first occurrence of the element passed in the list after position index. It returns -1 if the element is not present in the list.
Syntax:
public int indexOf(E e, int index)
- Parameters: The function accepts two parameters which are described below:
- index: specifies the index from which the occurrence is to be searched.
- e: specifies the element whose first occurrence from position index is to be returned.
Return Value: The function returns the first occurrence of the element after position index. It returns -1 if the element is not present in the list.
Exceptions: The function throws an IndexOutOfBoundsException if the specified index is negative.
Below programs illustrate the above function:
Program 1:
Java
// Java Program to illustrate the CopyOnWriteArrayList
// indexOf() method in Java
import java.util.concurrent.CopyOnWriteArrayList;
import java.util.*;
public class GFG {
public static void main(String[] args)
{
// create object of CopyOnWriteArrayList
CopyOnWriteArrayList<Integer> ArrLis
= new CopyOnWriteArrayList<Integer>();
// Add elements
ArrLis.add(32);
ArrLis.add(67);
ArrLis.add(67);
ArrLis.add(67);
// print CopyOnWriteArrayList
System.out.println("CopyOnWriteArrayList: "
+ ArrLis);
// first occurrence of 67 from 2nd index
System.out.println("indexOf value: "
+ ArrLis.indexOf(67, 2));
}
}
Output:
CopyOnWriteArrayList: [32, 67, 67, 67]
indexOf value: 2
Program 2:
Java
// Java Program to illustrate the CopyOnWriteArrayList
// indexOf() method in Java
import java.util.concurrent.CopyOnWriteArrayList;
import java.util.*;
public class GFG {
public static void main(String[] args)
{
// create object of CopyOnWriteArrayList
CopyOnWriteArrayList<Integer> ArrLis
= new CopyOnWriteArrayList<Integer>();
// Add elements
ArrLis.add(32);
ArrLis.add(67);
ArrLis.add(67);
ArrLis.add(100);
// print CopyOnWriteArrayList
System.out.println("CopyOnWriteArrayList: "
+ ArrLis);
// -1 is out of range, hence exception
System.out.println("indexOf value: "
+ ArrLis.indexOf(-1, 200));
}
}
Output:
Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: -1
at java.util.concurrent.CopyOnWriteArrayList.indexOf(CopyOnWriteArrayList.java:198)
at java.util.concurrent.CopyOnWriteArrayList.indexOf(CopyOnWriteArrayList.java:263)
at GFG.main(GFG.java:24)