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Java 15 Features Intro

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🎉 Java 15 – New Features With a Twist of Humor ☕​

Release Date: September 15th, 2020
Frequency: Every 6 months, like clockwork.
Mood: Still Java, but cooler.

Brace yourself, brave developer, for Java 15 is not just a number—it’s a tale of sealed secrets, invisible classes, and rebellious record-keepers. Grab your virtual coffee, and let's dive in! 🚀

1. 🛡️ Sealed Classes and Interfaces (Preview) – JEP 360​

Before Java 15, any class could walk up to your public class and say, “Yo, I’m your child now.” Not anymore!

Enter sealed classes and interfaces, the bouncers of Java inheritance. Using the sealed keyword, you can now whitelist the classes allowed to extend or implement your base class/interface. Total control, baby. ✋

Here's how the VIP list looks:

sealed class Account
    permits CurrentAccount, SavingAccount, LoanAccount {
}

final class CurrentAccount extends Account {}
non-sealed class SavingAccount extends Account {}
sealed class LoanAccount extends Account permits HomeloanAccount, AutoloanAccount {}

final class HomeloanAccount extends LoanAccount{}
final class AutoloanAccount extends LoanAccount{}

Translation:

  • sealed = “You can’t sit with us… unless you’re on the list.”
  • final = “End of the line.”
  • non-sealed = “Free spirit. Do what you want.”

📚 Read More: Sealed Classes and Interfaces

2. 🔏 EdDSA Algorithm – JEP 339​

Need a signature that’s both faster and more secure than your doctor’s? Say hello to EdDSA (Edwards-Curve Digital Signature Algorithm)!

KeyPairGenerator kpg = KeyPairGenerator.getInstance("Ed25519");
KeyPair kp = kpg.generateKeyPair();

byte[] msg = "test_string".getBytes(StandardCharsets.UTF_8);

Signature sig = Signature.getInstance("Ed25519");
sig.initSign(kp.getPrivate());
sig.update(msg);
byte[] s = sig.sign();

String encodedString = Base64.getEncoder().encodeToString(s);
System.out.println(encodedString);

It's like a digital wax seal for your data. Fancy AND secure. 🔐

📚 Read More: Java EdDSA (Ed25519 / Ed448) Example

3. 🕶️ Hidden Classes – JEP 371​

These aren’t just shy classes. They’re invisible ninjas of the JVM. 🥷

Hidden classes can’t be accessed by other classes' bytecode and are perfect for frameworks that create classes at runtime.

Why hide them?

  • So your framework internals don’t clutter the JVM.
  • So you can unload them guilt-free.
  • So you don’t have to rely on that sketchy sun.misc.Unsafe guy anymore.

4. 🌟 Other Enhancements (Cool Stuff Corner)​

4.1 🧩 Pattern Matching for instanceof (Second Preview) – JEP 375​

Less boilerplate. More magic. You can now combine type checks and casting in a single line. 🎯

if (obj instanceof String s) {
    // s is now a String you can use directly. No casting. Woohoo!
}

// Real-world example
if(customer instanceof PersonalCustomer pCustomer) {
    customerName = String.join(" ",
        pCustomer.getFirstName(), 
        pCustomer.getMiddleName(), 
        pCustomer.getLastName());
} else if(customer instanceof BusinessCustomer bCustomer) {
    customerName = bCustomer.getLegalName();
}

📚 Read More: Pattern Matching for instanceof

4.2 🪦 Removed Nashorn JavaScript Engine – JEP 372​

First introduced in Java 8, Nashorn was Java’s answer to “Hey, let’s do JS too!” But ECMAScript evolves faster than a Java developer rejecting frontend tasks. 😅

So Nashorn’s out. Bye bye, JS in JVM. 👋

4.3 📡 Reimplement Legacy DatagramSocket API – JEP 373​

The DatagramSocket API got a glow-up! ✨

  • Easier debugging
  • Friendly with upcoming virtual threads
  • Helps Project Loom nap better 😴

4.4 🧾 Records (Second Preview) – JEP 384​

Records are Java’s way of saying: “Let’s stop writing boilerplate and just store some dang data!”

record User(String name, int age) {}

Boom! You get:

  • constructor
  • getters
  • equals()
  • hashCode()
  • toString()

And yes, trying to mutate fields via reflection now throws an IllegalAccessException. Sorry hackers! 🚫

4.5 🧵 Text Blocks – JEP 378​

Multi-line strings are here, and they’re beautiful. No more \n, no more +, just triple quotes and peace. ✌️

String dbSchema =   """
        CREATE TABLE 'TEST'.'EMPLOYEE'
        (
          'ID' INT NOT NULL DEFAULT 0 ,
          'FIRST_NAME' VARCHAR(100) NOT NULL ,
          'LAST_NAME' VARCHAR(100) NULL ,
          'STAT_CD' TINYINT NOT NULL DEFAULT 0
        );
        """;

📚 Read More: Text Blocks

4.6 🗑️ Garbage Collection – JEPs 377 & 379​

  • ZGC and Shenandoah are now official, not just experimental. 🧪❌
  • G1 is still the default.

Java’s garbage collectors just keep getting smarter (unlike your roommate).

5. 🏁 Conclusion​

Java 15 brings us:

  • 🛡️ Sealed classes
  • 🕶️ Hidden classes
  • 🧾 Records
  • 🧵 Text blocks
  • 🔏 EdDSA signatures
  • 💀 Goodbye Nashorn
  • 🧠 Smarter pattern matching
  • 🗑️ Upgraded GCs

Whether you’re a curious coder or a battle-hardened Java warrior, Java 15 has a little something for everyone.

Stay sealed, hidden, and immutable, my friends. ☕💻

Happy Learning!! 🎉