Java 24 in Action: Real-World Use Cases and Problem-Solving Examples

1. Efficient Memory Management with Foreign Function & Memory API

Using the Foreign Function & Memory API for high-performance data processing

Processing large datasets in Java has always been memory-intensive. The Foreign Function & Memory API in Java 24 enables direct memory access and efficient data manipulation.

Problem with Traditional Approach:

// Old approach - loads entire dataset into heap memory
public class DataProcessor {
    public void processLargeDataset(String filePath) {
        try {
            byte[] data = Files.readAllBytes(Path.of(filePath));
            // Process data in memory
            for (int i = 0; i < data.length; i++) {
                // Memory-intensive operation
                data[i] = processByte(data[i]);
            }
            Files.write(Path.of("output.dat"), data);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

Solution with Java 24 Foreign Function & Memory API:

public class EfficientDataProcessor {
    // Modern record for processing metadata
    record ProcessingMetadata(long size, int chunkSize) {}
    
    // Modern sealed interface for processing operations
    sealed interface ProcessingOperation {
        record Transform(byte[] transformMatrix) implements ProcessingOperation {}
        record Filter(byte threshold) implements ProcessingOperation {}
        record Compress(int level) implements ProcessingOperation {}
    }

    public void processLargeDataset(String filePath, ProcessingOperation operation) {
        try (var arena = Arena.ofConfined()) {
            // Modern pattern matching for file operations
            var result = switch (operation) {
                case ProcessingOperation.Transform transform -> 
                    processWithTransform(arena, filePath, transform.transformMatrix());
                case ProcessingOperation.Filter filter -> 
                    processWithFilter(arena, filePath, filter.threshold());
                case ProcessingOperation.Compress compress -> 
                    processWithCompression(arena, filePath, compress.level());
            };
            
            // Write processed data using modern try-with-resources
            try (var channel = FileChannel.open(
                Path.of("output.dat"), 
                StandardOpenOption.CREATE, 
                StandardOpenOption.WRITE)) {
                channel.write(result.asByteBuffer());
            }
        } catch (IOException e) {
            throw new UncheckedIOException(e);
        }
    }

    private MemorySegment processWithTransform(Arena arena, String filePath, byte[] matrix) {
        // Implementation using modern memory access patterns
        var metadata = readFileMetadata(filePath);
        var buffer = arena.allocate(metadata.size());
        
        // Process data with transformation matrix
        return buffer;
    }

    private ProcessingMetadata readFileMetadata(String filePath) {
        // Implementation for reading file metadata
        return new ProcessingMetadata(1024 * 1024 * 100, 8192); // 100MB file, 8KB chunks
    }

    public static void main(String[] args) {
        var processor = new EfficientDataProcessor();
        processor.processLargeDataset("input.dat", 
            new ProcessingOperation.Transform(new byte[]{1, 2, 3, 4}));
    }
}

2. Thread-Safe Context Propagation with Scoped Values

Using Scoped Values for reliable context management

Managing context across async operations has been challenging. Java 24's Scoped Values provide a safer alternative to ThreadLocal for context propagation.

Problem with Traditional Approach:

// Old approach using ThreadLocal - prone to memory leaks
public class RequestContext {
    private static final ThreadLocal requestId = 
        ThreadLocal.withInitial(() -> "");
    private static final ThreadLocal currentUser = 
        ThreadLocal.withInitial(() -> null);
    
    public static void setContext(String reqId, User user) {
        requestId.set(reqId);
        currentUser.set(user);
    }
    
    public static void clearContext() {
        requestId.remove();
        currentUser.remove();
    }
    
    public static void processRequest() {
        try {
            // Set context
            setContext("REQ-123", new User("john"));
            
            // Async operation - context lost!
            CompletableFuture.runAsync(() -> {
                // ThreadLocal values don't propagate
                System.out.println("Request ID: " + requestId.get());
            });
        } finally {
            clearContext(); // Must remember to clear
        }
    }
}

Solution with Java 24 Scoped Values:

public class ModernRequestContext {
    // Modern sealed interface for context values
    sealed interface ContextValue {
        record RequestId(String id) implements ContextValue {}
        record User(String name, String role) implements ContextValue {}
        record Tenant(String id, String name) implements ContextValue {}
    }

    // Modern scoped values with type safety
    private static final ScopedValue REQUEST_ID = ScopedValue.newInstance();
    private static final ScopedValue CURRENT_USER = ScopedValue.newInstance();
    private static final ScopedValue CURRENT_TENANT = ScopedValue.newInstance();

    // Modern record for request context
    record RequestContext(
        RequestId requestId,
        User user,
        Tenant tenant
    ) {}

    public void processRequest(RequestContext context) {
        // Modern pattern matching with scoped values
        ScopedValue.where(REQUEST_ID, context.requestId())
            .where(CURRENT_USER, context.user())
            .where(CURRENT_TENANT, context.tenant())
            .run(() -> {
                // Process request with modern switch expressions
                var result = switch (context.user().role()) {
                    case "admin" -> processAdminRequest();
                    case "user" -> processUserRequest();
                    default -> throw new IllegalStateException("Unknown role");
                };

                // Modern async processing with structured concurrency
                try (var scope = new StructuredTaskScope.ShutdownOnFailure()) {
                    var future = scope.fork(() -> processAsync(result));
                    scope.join();
                    future.get();
                } catch (InterruptedException e) {
                    Thread.currentThread().interrupt();
                }
            });
    }

    private String processAdminRequest() {
        return "Admin request processed";
    }

    private String processUserRequest() {
        return "User request processed";
    }

    private CompletableFuture processAsync(String result) {
        return CompletableFuture.completedFuture(result);
    }

    public static void main(String[] args) {
        var context = new RequestContext(
            new ContextValue.RequestId("REQ-123"),
            new ContextValue.User("john", "admin"),
            new ContextValue.Tenant("T1", "Acme Corp")
        );
        
        new ModernRequestContext().processRequest(context);
    }
}

3. Enhanced Pattern Matching with Record Patterns

Using Record Patterns for more expressive data handling

Java 24 introduces Record Patterns, making it easier to work with record types and nested data structures.

Problem with Traditional Approach:

// Old approach - verbose pattern matching
public class DataProcessor {
    public void processData(Object data) {
        if (data instanceof Point point) {
            int x = point.x();
            int y = point.y();
            processPoint(x, y);
        } else if (data instanceof Rectangle rect) {
            Point topLeft = rect.topLeft();
            Point bottomRight = rect.bottomRight();
            processRectangle(topLeft.x(), topLeft.y(), 
                          bottomRight.x(), bottomRight.y());
        }
    }
}

Solution with Java 24 Record Patterns:

public class ModernDataProcessor {
    // Modern record types
    record Point(int x, int y) {}
    record Rectangle(Point topLeft, Point bottomRight) {}
    record Circle(Point center, int radius) {}
    
    // Modern sealed interface for shapes
    sealed interface Shape {
        record Square(Point topLeft, int size) implements Shape {}
        record Triangle(Point p1, Point p2, Point p3) implements Shape {}
    }

    public void processData(Object data) {
        // Modern record patterns with nested matching
        switch (data) {
            case Point(int x, int y) -> 
                processPoint(x, y);
            case Rectangle(Point(int x1, int y1), Point(int x2, int y2)) -> 
                processRectangle(x1, y1, x2, y2);
            case Circle(Point(int cx, int cy), int r) -> 
                processCircle(cx, cy, r);
            case Shape.Square(Point(int x, int y), int size) -> 
                processSquare(x, y, size);
            case Shape.Triangle(Point(int x1, int y1), 
                              Point(int x2, int y2), 
                              Point(int x3, int y3)) -> 
                processTriangle(x1, y1, x2, y2, x3, y3);
            default -> 
                throw new IllegalArgumentException("Unknown shape");
        }
    }

    private void processPoint(int x, int y) {
        System.out.printf("Processing point at (%d, %d)%n", x, y);
    }

    private void processRectangle(int x1, int y1, int x2, int y2) {
        System.out.printf("Processing rectangle from (%d, %d) to (%d, %d)%n", 
                         x1, y1, x2, y2);
    }

    private void processCircle(int cx, int cy, int r) {
        System.out.printf("Processing circle at (%d, %d) with radius %d%n", 
                         cx, cy, r);
    }

    private void processSquare(int x, int y, int size) {
        System.out.printf("Processing square at (%d, %d) with size %d%n", 
                         x, y, size);
    }

    private void processTriangle(int x1, int y1, int x2, int y2, int x3, int y3) {
        System.out.printf("Processing triangle with points (%d, %d), (%d, %d), (%d, %d)%n", 
                         x1, y1, x2, y2, x3, y3);
    }

    public static void main(String[] args) {
        var processor = new ModernDataProcessor();
        
        // Test with various shapes
        processor.processData(new Point(10, 20));
        processor.processData(new Rectangle(new Point(0, 0), new Point(100, 100)));
        processor.processData(new Circle(new Point(50, 50), 25));
        processor.processData(new Shape.Square(new Point(0, 0), 50));
        processor.processData(new Shape.Triangle(
            new Point(0, 0), 
            new Point(50, 0), 
            new Point(25, 50)
        ));
    }
}

Conclusion and Best Practices

These examples demonstrate how Java 24's features solve real-world problems:

• Foreign Function & Memory API enables efficient memory management for large data processing
• Scoped Values offer a safer alternative to ThreadLocal for context propagation
• Record Patterns provide more expressive pattern matching for complex data structures

Remember these best practices:

• Always use try-with-resources with Arena instances when using Foreign Memory API
• Design your Scoped Values to be immutable
• Use Record Patterns to simplify complex data structure handling
• Consider performance implications when choosing between heap and off-heap memory