Java 16

// Concise type checking and casting
if (obj instanceof String s) {
    System.out.println("Length: " + s.length());
}

// Works with negation
if (!(obj instanceof String s)) {
    throw new IllegalArgumentException("Expected String");
}
// s not in scope here

// Combines with && operator
if (obj instanceof String s && s.length() > 10) {
    System.out.println(s.toUpperCase());
}

public double getPerimeter(Shape shape) {
    if (shape instanceof Circle c) {
        return 2 * Math.PI * c.radius();
    } else if (shape instanceof Rectangle r) {
        return 2 * (r.width() + r.height());
    } else if (shape instanceof Triangle t) {
        return t.side1() + t.side2() + t.side3();
    }
    throw new IllegalArgumentException("Unknown shape");
}

public record Point(int x, int y) {}

// Auto-generated:
// - Constructor: Point(int x, int y)
// - Accessors: x(), y()
// - equals(), hashCode(), toString()

public record Range(int min, int max) {
    // Compact constructor for validation
    public Range {
        if (min > max) {
            throw new IllegalArgumentException("min must be <= max");
        }
    }
}

public record Point(int x, int y) {
    public double distanceFromOrigin() {
        return Math.sqrt(x * x + y * y);
    }

    public Point translate(int dx, int dy) {
        return new Point(x + dx, y + dy);
    }
}

public sealed interface Expression
    permits Value, Addition, Multiplication {
}

public record Value(int value) implements Expression {}
public record Addition(Expression left, Expression right) implements Expression {}
public record Multiplication(Expression left, Expression right) implements Expression {}

// Pattern matching with sealed types (preview)
public int eval(Expression expr) {
    return switch (expr) {
        case Value v -> v.value();
        case Addition a -> eval(a.left()) + eval(a.right());
        case Multiplication m -> eval(m.left()) * eval(m.right());
        // No default needed - compiler knows all cases covered!
    };
}

# Windows installer
jpackage --input target/ \
         --name MyApp \
         --main-jar myapp.jar \
         --main-class com.example.Main \
         --type msi \
         --icon myicon.ico \
         --win-menu \
         --win-shortcut

# macOS app bundle
jpackage --input target/ \
         --name MyApp \
         --main-jar myapp.jar \
         --type dmg \
         --icon myicon.icns

# Linux package
jpackage --input target/ \
         --name myapp \
         --main-jar myapp.jar \
         --type deb

import jdk.incubator.vector.*;

static final VectorSpecies<Float> SPECIES = FloatVector.SPECIES_PREFERRED;

void vectorComputation(float[] a, float[] b, float[] c) {
    int i = 0;
    int upperBound = SPECIES.loopBound(a.length);

    for (; i < upperBound; i += SPECIES.length()) {
        // Vectorized operations
        FloatVector va = FloatVector.fromArray(SPECIES, a, i);
        FloatVector vb = FloatVector.fromArray(SPECIES, b, i);
        FloatVector vc = va.mul(vb);
        vc.intoArray(c, i);
    }

    // Scalar tail
    for (; i < a.length; i++) {
        c[i] = a[i] * b[i];
    }
}

import jdk.incubator.foreign.*;

CLinker linker = CLinker.getInstance();
SymbolLookup stdlib = CLinker.systemLookup();

// Call strlen from C standard library
MethodHandle strlen = linker.downcallHandle(
    stdlib.lookup("strlen").get(),
    MethodType.methodType(long.class, MemoryAddress.class),
    FunctionDescriptor.of(C_LONG, C_POINTER)
);

try (MemorySegment str = CLinker.toCString("Hello", ResourceScope.newConfinedScope())) {
    long len = (long) strlen.invoke(str.address());
    System.out.println("Length: " + len); // 5
}

import jdk.incubator.foreign.*;

try (ResourceScope scope = ResourceScope.newConfinedScope()) {
    MemorySegment segment = MemorySegment.allocateNative(1024, scope);

    // Write data
    MemoryAccess.setIntAtOffset(segment, 0, 42);
    MemoryAccess.setDoubleAtOffset(segment, 4, 3.14);

    // Read data
    int intValue = MemoryAccess.getIntAtOffset(segment, 0);
    double doubleValue = MemoryAccess.getDoubleAtOffset(segment, 4);
}
// Memory automatically freed when scope closes

// ❌ FAILS in Java 16+
import sun.misc.Unsafe;
Unsafe unsafe = Unsafe.getUnsafe();

// ✅ Use standard alternatives
// - java.lang.invoke.MethodHandles for reflection
// - java.lang.invoke.VarHandle for low-level operations
// - Foreign-Memory Access API for off-heap memory

java --illegal-access=warn -jar myapp.jar
# Shows warnings for illegal access