Last Updated : 10 Dec, 2024
In Java, the lastIndexOf() method is used to find the index of the last occurrence of a specified element in an ArrayList.
Example 1: Here, we will use the lastIndexOf() method to find the index of the last occurrence of a specific element in an ArrayList of integers.
Java
// Java program to demonstrate the use of
// lastIndexOf() method with Integers
import java.util.ArrayList;
public class GFG {
public static void main(String[] args) {
// Creating an ArrayList of Integers
ArrayList<Integer> n = new ArrayList<>();
// Adding elements to the ArrayList
n.add(21);
n.add(22);
n.add(23);
// Using lastIndexOf() to find the last index of 20
int i= n.lastIndexOf(22);
System.out.println("The last index of 22 is: " + i);
}
}
The last index of 22 is: 1Syntax of ArrayList
lastIndexOf()
Method
public int lastIndexOf(Object o)
Example 2: Here, we use the lastIndexOf() method to find the last occurrence of an element in an ArrayList of strings.
Java
// Java program to demonstrate the use of
// lastIndexOf() method for Strings
import java.util.ArrayList;
public class GFG {
public static void main(String[] args) {
// Creating an ArrayList of Strings
ArrayList<String> f = new ArrayList<>();
// Adding elements to the ArrayList
f.add("Apple");
f.add("Banana");
f.add("Orange");
// Using lastIndexOf() to find the
// last index of "Orange"
int i = f.lastIndexOf("Orange");
System.out.println("The last index of Orange is: " + i);
}
}
The last index of Orange is: 2
Example 3: In this example, we will use the lastIndexOf() method with an ArrayList of custom objects. Here, we will find the last index of a specific object in the list.
Java
// Java program to demonstrate the use of
// lastIndexOf() method with custom Objects
import java.util.ArrayList;
class Person {
String n;
int a;
// Constructor to initialize Person object
public Person(String n, int a) {
this.n = n;
this.a = a;
}
// Overriding equals() to compare Person
// objects based on name and age
@Override
public boolean equals(Object o) {
if (this == o)
return true;
if (o == null || getClass() != o.getClass())
return false;
Person p = (Person) o;
return a == p.a && n.equals(p.n);
}
}
public class Main {
public static void main(String[] args) {
// Creating an ArrayList of Person objects
ArrayList<Person> p = new ArrayList<>();
// Adding elements to the ArrayList
p.add(new Person("Sweta", 24));
p.add(new Person("Amiya", 27));
p.add(new Person("Gudly", 23));
// Using lastIndexOf() to find the
// last index of a Person object
Person personToFind = new Person("Sweta", 24);
int i = p.lastIndexOf(personToFind);
System.out.println("The last index of Sweta is: " + i);
}
}
The last index of Sweta is: 0
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