JDK 9新特性之VarHandle

// -- This file was mechanically generated: Do not edit! -- //
final class VarHandleByteArrayAsChars extends VarHandleByteArrayBase {
	static final JavaNioAccess NIO_ACCESS = SharedSecrets.getJavaNioAccess();
	
	static final int ALIGN = Character.BYTES - 1;
	
	static final ScopedMemoryAccess SCOPED_MEMORY_ACCESS = ScopedMemoryAccess.getScopedMemoryAccess();
	
	@ForceInline
	static char convEndian(boolean big, char n) {
		return big == BE ? n : Character.reverseBytes(n);
	}
	
	static abstract sealed class ByteArrayViewVarHandle extends VarHandle {
	}
	
	static final class ArrayHandle extends ByteArrayViewVarHandle {
		// 省略方法若干，下同
		static final VarForm FORM = new VarForm(ArrayHandle.class, byte[].class, char.class, int.class);
	}
	
	static final class ByteBufferHandle extends ByteArrayViewVarHandle {
		static final VarForm FORM = new VarForm(ByteBufferHandle.class, ByteBuffer.class, char.class, int.class);
	}
}

enum AccessType {
	GET(Object.class),
	SET(void.class),
	COMPARE_AND_SET(boolean.class),
	COMPARE_AND_EXCHANGE(Object.class),
	GET_AND_UPDATE(Object.class);
}

public enum AccessMode {
	// 省略引用AccessType
	GET("get", GET),
	SET("set", SET),
	GET_VOLATILE("getVolatile", GET),
	SET_VOLATILE("setVolatile", SET),
	GET_ACQUIRE("getAcquire", GET),
	SET_RELEASE("setRelease", SET),
	GET_OPAQUE("getOpaque", GET),
	SET_OPAQUE("setOpaque", SET),
	COMPARE_AND_SET("compareAndSet", COMPARE_AND_SET),
	COMPARE_AND_EXCHANGE("compareAndExchange", COMPARE_AND_EXCHANGE),
	COMPARE_AND_EXCHANGE_ACQUIRE("compareAndExchangeAcquire", COMPARE_AND_EXCHANGE),
	COMPARE_AND_EXCHANGE_RELEASE("compareAndExchangeRelease", COMPARE_AND_EXCHANGE),
	WEAK_COMPARE_AND_SET_PLAIN("weakCompareAndSetPlain", COMPARE_AND_SET),
	WEAK_COMPARE_AND_SET("weakCompareAndSet", COMPARE_AND_SET),
	WEAK_COMPARE_AND_SET_ACQUIRE("weakCompareAndSetAcquire", COMPARE_AND_SET),
	WEAK_COMPARE_AND_SET_RELEASE("weakCompareAndSetRelease", COMPARE_AND_SET),
	GET_AND_SET("getAndSet", GET_AND_UPDATE),
	GET_AND_SET_ACQUIRE("getAndSetAcquire", GET_AND_UPDATE),
	GET_AND_SET_RELEASE("getAndSetRelease", GET_AND_UPDATE),
	GET_AND_ADD("getAndAdd", GET_AND_UPDATE),
	GET_AND_ADD_ACQUIRE("getAndAddAcquire", GET_AND_UPDATE),
	GET_AND_ADD_RELEASE("getAndAddRelease", GET_AND_UPDATE),
	GET_AND_BITWISE_OR("getAndBitwiseOr", GET_AND_UPDATE),
	GET_AND_BITWISE_OR_RELEASE("getAndBitwiseOrRelease", GET_AND_UPDATE),
	GET_AND_BITWISE_OR_ACQUIRE("getAndBitwiseOrAcquire", GET_AND_UPDATE),
	GET_AND_BITWISE_AND("getAndBitwiseAnd", GET_AND_UPDATE),
	GET_AND_BITWISE_AND_RELEASE("getAndBitwiseAndRelease", GET_AND_UPDATE),
	GET_AND_BITWISE_AND_ACQUIRE("getAndBitwiseAndAcquire", GET_AND_UPDATE),
	GET_AND_BITWISE_XOR("getAndBitwiseXor", GET_AND_UPDATE),
	GET_AND_BITWISE_XOR_RELEASE("getAndBitwiseXorRelease", GET_AND_UPDATE),
	GET_AND_BITWISE_XOR_ACQUIRE("getAndBitwiseXorAcquire", GET_AND_UPDATE),
	;

	private final String methodName;
	private final AccessType at;
}

@Slf4j
public class VarHandleDemo {
	private int x; // 共享变量
	private static VarHandle X;

	static {
		try {
			// 初始化VarHandle：需指定要保护的变量，某个类中的 共享变量名名 共享变量类型。
			// 注意到这里int基础类型也可以获取到class类型
			X = MethodHandles.lookup().findVarHandle(VarHandleDemo.class, "x", int.class);
		} catch (NoSuchFieldException | IllegalAccessException e) {
			log.error("fail: {}", e.getMessage());
		}
	}

	public static void main(String[] args) throws NoSuchFieldException, IllegalAccessException {
		VarHandleDemo obj = new VarHandleDemo();
		X.set(obj, 10);
		Object o = X.get(obj);
		System.out.println(o);
	}
}

public class VarHandleDemo {
	public int publicVar = 1;
	protected int protectedVar = 2;
	private int privateVar = 3;
	public int[] arrayData = new int[]{1, 2, 3};
	
	@Override
	public String toString() {
		return "VarHandleDemo {" + "publicVar=" + publicVar + ", protectedVar=" + protectedVar + ", privateVar=" + privateVar + ", arrayData=" + Arrays.toString(arrayData) + '}';
	}
	
	private static void protectedDemo() throws NoSuchFieldException, IllegalAccessException {
		VarHandleDemo demo = new VarHandleDemo();
		VarHandle varHandle = MethodHandles.privateLookupIn(VarHandleDemo.class, MethodHandles.lookup()).findVarHandle(VarHandleDemo.class, "protectedVar", int.class);
		VarHandle varHandle0 = MethodHandles.privateLookupIn(VarHandleDemo.class, MethodHandles.lookup()).findVarHandle(VarHandleDemo.class, "publicVar", int.class);
		// publicLookup 访问 private 属性，报错：IllegalAccessException: member is private
		// VarHandle varHandle1 = MethodHandles.publicLookup().in(VarHandleDemo.class).findVarHandle(VarHandleDemo.class, "privateVar", int.class);
		// publicLookup 访问 protected 属性，报错：IllegalAccessException: member is protected
		// VarHandle varHandle2 = MethodHandles.publicLookup().in(VarHandleDemo.class).findVarHandle(VarHandleDemo.class, "protectedVar", int.class);
	    varHandle0.set(demo, 22);
	    System.out.println(demo);
	}


	
	public static void main(String[] args) throws NoSuchFieldException, IllegalAccessException {
		protectedDemo();
		arrayDemo();
	}
}

private static void arrayDemo() {
	VarHandleDemo demo = new VarHandleDemo();
	// int数组class
	VarHandle arrayVarHandle = MethodHandles.arrayElementVarHandle(int[].class);
	// 第0个索引，如果是1，则更新为11
	arrayVarHandle.compareAndSet(demo.arrayData, 0, 1, 11);
	// 第1个索引，如果是3（本来是2），则更新为22（不会更新）
	arrayVarHandle.compareAndSet(demo.arrayData, 1, 3, 22);
	System.out.println(demo);
}