Java 21¶

Java 21 (2023) - LTS:

Virtual Threads (standard): The preview feature from Java 19 and 20 became standard.

Thread.startVirtualThread(() -> {
    System.out.println("Running in a virtual thread");
});

Pattern Matching for switch (standard): The preview feature from previous versions became standard.

static String formatterPatternSwitch(Object obj) {
    return switch (obj) {
        case Integer i -> String.format("int %d", i);
        case Long l    -> String.format("long %d", l);
        case Double d  -> String.format("double %f", d);
        case String s  -> String.format("String %s", s);
        case null      -> "null";
        default        -> obj.toString();
    };
}

Record Patterns (standard): The preview feature from Java 19 became standard.
Sequenced Collections: New interfaces for collections with a defined encounter order.

SequencedCollection<String> list = new ArrayList<>(List.of("a", "b", "c"));
String first = list.getFirst();
String last = list.getLast();

Unnamed Classes and Instance Main Methods: Simplified syntax for small programs, useful for learning and testing.

void main() {
    System.out.println("Hello, World!");
}