Java 8 to Java 25: Major Features Timeline and Evolution Guide.

// Imperative Java 7 way vs Declarative Java 8 way
List<String> premiumUserEmails = users.stream()
    .filter(u -> u.getBalance() > 1000)
    .map(User::getEmail)
    .collect(Collectors.toList());

// Convenient, immutable collections
List<String> activeRoles = List.of("ADMIN", "DEVELOPER", "AUDITOR");
Map<String, Integer> timeouts = Map.of("read", 5000, "connect", 2000);

// 1. One-line immutable DTO Record
public record UserDTO(Long id, String email, BigDecimal balance) {}

// 2. Pattern Matching for instanceof
if (response instanceof SuccessResponse success) {
    System.out.println("Status: " + success.getStatusCode()); // Directly usable!
}

// 3. Switch Expressions
String label = switch (orderStatus) {
    case PENDING -> "Awaiting Payment";
    case SHIPPED, DELIVERED -> "Completed";
    default -> "Unknown";
};

// Only these three classes are permitted to implement PaymentEvent!
public sealed interface PaymentEvent permits PaymentSuccess, PaymentFailed, PaymentPending {}

public final class PaymentSuccess implements PaymentEvent {}
public final class PaymentFailed implements PaymentEvent { String reason; }
public final class PaymentPending implements PaymentEvent {}

// 1. Virtual Threads Executor: 100,000 concurrent tasks effortlessly
try (var executor = Executors.newVirtualThreadPerTaskExecutor()) {
    IntStream.range(0, 100_000).forEach(i -> {
        executor.submit(() -> {
            Thread.sleep(Duration.ofSeconds(1)); // Unmounts from carrier thread!
            return i;
        });
    });
}

// 2. Pattern Matching with Switch & Record Deconstruction
static String process(Object obj) {
    return switch (obj) {
        case UserDTO(Long id, String email, BigDecimal balance) when balance.compareTo(BigDecimal.ZERO) < 0 ->
            "Negative balance user: " + email;
        case UserDTO(Long id, String email, BigDecimal balance) ->
            "Active user: " + email;
        case String s -> "Raw string: " + s;
        default -> "Other type";
    };
}

// Group incoming numbers into fixed sliding batches of 3
List<List<Integer>> windows = List.of(1, 2, 3, 4, 5, 6, 7, 8)
    .stream()
    .gather(Gatherers.windowSliding(3))
    .toList();
// Output: [[1, 2, 3], [2, 3, 4], [3, 4, 5], ...]