Java 21 Features

Java 21 Features

String Templates (Preview) 

Ex:

String name = "BSS Java";

String greeting = STR."Hello, \{name}!";

Sequenced Collections 

- SequencedCollection

Ex:

SequencedCollection<String> names = new ArrayList<>();

names.addFirst("Alice");  

names.addLast("Bob");

names.getFirst();

names.getLast();

names.removeFirst(); 

names.removeLast();

- SequencedSet

Ex:

SequencedCollection<String> set = new LinkedHashSet<>();

// Adding elements

set.addFirst("Alice");

set.addLast("Bob");

set.getFirst();

set.getLast();

set.removeFirst();

set.removeLast();

- SequencedMap

putFirst(K key, V value)

putLast(K key, V value)

pollFirstEntry()

pollLastEntry()

firstEntry()

lastEntry()

Ex:

SequencedMap<String, Integer> map = new LinkedHashMap<>();

// Adding entries

map.putFirst("Alice", 25);

map.putLast("Bob", 30);

map.firstEntry()

map.lastEntry()

map.pollFirstEntry();

map.pollLastEntry();

Record Patterns 

Ex:

if (obj instanceof Point(int x, int y)) {

    System.out.println(x + y);

}

Pattern Matching for switch

Ex:

switch (obj) {

    case String s -> System.out.println("It's a string: " + s);

    case null -> System.out.println("It's null");

    default -> System.out.println("Unknown type");

}

Unnamed Patterns and Variables (Preview)

Unnamed Classes and Instance main Methods (Preview)

Ex:

// Save as Example.java

void main() {

    System.out.println("Hello, Java 21!");

}

>java --enable-preview --source 21 Example.java

Scoped Values (Preview)