How to Mapping code logic using Stream API

Stream API in Java provides a powerful way to work with collections and other data sources. Mapping is one of the key operations available in the Stream API, used to transform elements of a stream. Here's a step-by-step guide on how to use the map function with the Stream API:
Import Required Classes :

Create a Stream:
You can create a stream from various sources, like collections, arrays, or generator functions. For example, creating a stream from a list:
Apply the map Function:
Use the map function to transform each element of the stream. For instance, to convert each name to uppercase:
Collect the Results:
Finally, you can collect the transformed stream back into a list or another collection:
Complete Example:
Here’s a complete example demonstrating how to use the map function with the Stream API:
import java.util.Arrays; import java.util.List; import java.util.stream.Collectors; public class StreamMapExample { public static void main(String[] args) { // Create a list of names List<String> names = Arrays.asList("a14mk", "manoj", "Jack"); // Convert the list to a stream List<String> upperCaseNames = names.stream() // Apply the map function to transform each name to uppercase .map(String::toUpperCase) // Collect the results back into a list .collect(Collectors.toList()); // Print the transformed list upperCaseNames.forEach(System.out::println); } }
Mapping with Complex Objects:
If you are working with a list of objects, you can use the map function to transform specific fields or create new objects. For example:
import java.util.Arrays; import java.util.List; import java.util.stream.Collectors; class Person { String name; int age; Person(String name, int age) { this.name = name; this.age = age; } public String getName() { return name; } public int getAge() { return age; } } public class StreamMapExample { public static void main(String[] args) { // Create a list of persons List<Person> people = Arrays.asList( new Person("a14mk", 25), new Person("manoj", 30), new Person("Jack", 35) ); // Transform the list to get a list of names List<String> names = people.stream().map(Person::getName).collect(Collectors.toList()); // Print the list of names names.forEach(System.out::println); } }
In this example, the map function is used to extract the names from a list of Person objects.