Java 21 Features:

1. Pattern Matching for Switch

Java 21 brings a powerful feature called Pattern Matching for Switch. It simplifies switch statements, making them more concise and readable. Check out an example:

 

// Before Java 21

String response = "yes";

  switch (response) {

  case "yes":

  case "yeah":

  System.out.println("You said yes!");

  break;

  case "no":

  case "nope":

  System.out.println("You said no!");

  break;

  default:

  System.out.println("Please choose.");

  }



}

In java 21:

// Java 21 Pattern Matching for Switch

  String response = "yes";

  switch (response) {

  case "yes", "yeah" -> System.out.println("You said yes!");

  case "no", "nope" -> System.out.println("You said no!");

  default -> System.out.println("Please choose.");

2. Unnamed Patterns and Variables

Java 21 introduces Unnamed Patterns and Variables, making your code more concise and expressive. Here’s a snippet to give you a taste:

String userInput = "User Input";

try {

int number = Integer.parseInt(userInput);

// Use 'number'

} catch (NumberFormatException ex) {

System.out.println("Invalid input: " + userInput);

}

Now, with Java 21, the above code can be rewritten as follows

String userInput = "User Input";

try {

int number = Integer.parseInt(userInput);

// Use 'number'

} catch (NumberFormatException _) {

System.out.println("Invalid input: " + userInput);

}

In this updated version, we no longer use the ‘ex’ variable; instead, we’ve replaced it with an underscore (_). This simple change helps streamline the code and makes it more concise.

 

3. Unnamed Classes and Instance Main Methods

Java 21 introduces a fresh approach to defining classes and instance main methods right in your code. Let’s take a quick look at how this feature operates:

// Java 21 Unnamed Classes and Instance Main Methods

public class UnnamedClassesDemo {

void main(String[] args) {

System.out.println("Hello from an unnamed class!");

}

}

 

4. String Templates in Java

Java 21 introduces String Templates, simplifying string concatenation. Take a look:

// Java (using String.format)

String name = "Sachin P";

String message = String.format("Welcome %s", Java);

In Java 21, you can create a message using this syntax:

String name = "Sachin P";

String message = STR."Welcome \{name}!";

 

5. Sequenced Collections in Java 21

Java 21 introduces Sequenced Collections, making it easier to work with ordered data. Here’s a glimpse:

List<Integer> list = new ArrayList<Integer>();

list.add(0);

list.add(1);

list.add(2);

// Fetch the first element (element at index 0)

int firstElement = list.get(0);

// Fetch the last element

int lastElement = list.get(list.size() - 1);

In Java 21, you can retrieve elements using the following code.

List<Integer> list = new ArrayList<Integer>();

list.add(0);

list.add(1);

list.add(2);

// Fetch the first element (element at index 0)

int firstElement = list.getFirst();

// Fetch the last element

int lastElement = list.getLast();