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 Javaimport 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)); }} |
CopyOnWriteArrayList: [32, 67, 67, 100] indexOf value: 1
Program 2:
Java
// Java Program to illustrate the CopyOnWriteArrayList// indexOf() method in Javaimport 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)); }} |
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 Javaimport 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 Javaimport 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)
