Java 9 features with examples

Category : Java | Sub Category : Java 9 introduced features | By Prasad Bonam Last updated: 2023-08-09 07:37:08 Viewed : 323

here are some Java 9 features with examples to illustrate their usage:

1. Module System (Project Jigsaw):

   Java 9 introduced the module system to improve modularity and encapsulation. Lets create a simple example with two modules, com.example.app and com.example.util:

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   // module-info.java in com.example.app
   module com.example.app {
       requires com.example.util;
   }
   
   // module-info.java in com.example.util
   module com.example.util {
       exports com.example.util;
   }
   

2. JShell (REPL):

   JShell allows you to interactively experiment with Java code:

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   // Launch JShell
   $ jshell
   
   // Example usage
   jshell> int x = 10;
   x ==> 10
   
   jshell> int y = 20;
   y ==> 20
   
   jshell> int sum = x + y;
   sum ==> 30
   

3. Factory Methods for Immutable Collections:

   Java 9 introduced factory methods for creating immutable collections:

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   // Creating an immutable list
   List<String> names = List.of("Alice", "Bob", "Charlie");
   
   // Creating an immutable set
   Set<Integer> numbers = Set.of(1, 2, 3);
   
   // Creating an immutable map
   Map<String, Integer> scores = Map.of("Alice", 100, "Bob", 90);
   

4. Private Interface Methods:

   Java 9 allows private methods in interfaces:

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   interface MyInterface {
       default void publicMethod() {
           privateMethod();
       }
   
       private void privateMethod() {
           System.out.println("Private method");
       }
   }
   

5. Stream API Enhancements:

   Java 9 added new methods to the Stream API:

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   List<Integer> numbers = List.of(1, 2, 3, 4, 5, 6);
   
   // takeWhile: takes elements while the condition is true
   List<Integer> evenNumbers = numbers.stream()
                                     .takeWhile(n -> n % 2 == 0)
                                     .collect(Collectors.toList());
   
   // dropWhile: drops elements while the condition is true
   List<Integer> afterThree = numbers.stream()
                                     .dropWhile(n -> n <= 3)
                                     .collect(Collectors.toList());
   

6. HTTP/2 Client:

   Java 9 introduced a new HTTP/2 client API:

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   import java.net.URI;
   import java.net.http.HttpClient;
   import java.net.http.HttpRequest;
   import java.net.http.HttpResponse;
   
   public class HttpExample {
       public static void main(String[] args) throws Exception {
           HttpClient client = HttpClient.newHttpClient();
           HttpRequest request = HttpRequest.newBuilder()
                   .uri(new URI("https://www.example.com"))
                   .build();
   
           HttpResponse<String> response = client.send(request, HttpResponse.BodyHandlers.ofString());
           System.out.println(response.body());
       }
   }
   

These examples provide a glimpse of the Java 9 features and how they can be used. Remember that you may need a Java 9 runtime environment to execute these examples.