Efficiently build a large array with MethodHandles
I have a need to construct a MethodHandle with signature (InternalContext)->Object[] from a List<MethodHandle> each with the signature (InternalContext)->Object.If the list is small <253...
View ArticleHow can I improve performance of Field.set (perhap using MethodHandles)?
I'm writing some code that calls Field.set and Field.get many many thousands of times. Obviously this is very slow because of the reflection.I want to see if I can improve performance using...
View ArticleOn signature polymorphic methods in Java-7
As far as I can tell, with the introduction of MethodHandle in Java 7 came the introduction of compiler-generated method overloads.The javadoc for MethodHandle states (I've trimmed the examples):Here...
View ArticleMethodHandle - What is it all about?
I am studying new features of JDK 1.7 and I just can't get it what MethodHandle is designed for? I understand (direct) invocation of the static method (and use of Core Reflection API that is...
View ArticleWeird behaviour of Java MethodHandle.invokeExact
Here is a minimal working example (requires Java 22 or later):(just using libc free for elaborating the behaviour)import java.lang.foreign.*;import java.lang.invoke.MethodHandle;public class Main {...
View ArticleMethodhandle private method called using findVirtual
Java doc of MethodHandle says that private method should invoke via findSpecial.But in the following example I am able to invoke it via findVirtual.Could somebody please explain what am I missing...
View ArticleWhat is the proper MethodType for invocation of a default constructor?
Suggest the code below. To me, it looks fine: I do obtain a MethodType, which takes no parameters as input, and produces an instance of A. The default constructor of a matchesthat description, in my...
View ArticleBuild error "com.android.tools.r8.internal.k2: MethodHandle.invoke and...
I have a module within my app that depends on org.tensorflow:tensorflow-lite:2.15.0 library. This library in turn depends on com.google.inject:guice:5.1.0 which is the source of the build error.Below...
View Articlelambdametafactory creation is quite slow compared to just using lambda
@Benchmarkpublic void testLambdaGeneration(Blackhole bh) { Function<Object, Object> function = a -> { if(a instanceof Alpha alpha) { return alpha.primitiveInt(); }else { throw new...
View ArticleBootstrapMethodError caused by LambdaConversionException caused by using...
I was trying to check if it is possible to use MethodHandle::invoke or MethodHandle::invokeExact as method references for a functional interface that accepts a MethodHandle and returns a generified...
View ArticleWhat does “MethodHandle::invoke” mean in Java? [duplicate]
Look the follow code:import java.lang.invoke.MethodHandle;public class Demo { interface TFunction<T, R> { R apply(T t) throws Throwable; } public class MyMethodHandle { public final native Object...
View ArticleIs there a problem with the javadoc for MethodHandles#exactInvoker?
I'm trying to understand the exactInvoker javadoc.It reads, in part:For example, to emulate an invokeExact call to a variable method handle M, extract its type T, look up the invoker method X for T,...
View ArticleJava poor performance with non-static `VarHandle`
I was investigating if replacing a java.lang.reflect.Field.get call with a VarHandle would improve performance, but instead it got slower.From benchmarking, I can see that when the VarHandle is static,...
View Article`MethodHandle` slower than Reflection when accessing Object
I would like to call a method via reflection in the most performant way possible.The method returns an Object.I've implemented this using both reflection and MethodHandles, I was expecting MethodHandle...
View Article`MethodHandle` slower than Reflection when accessing primitive
I would like to call a method via reflection in the most performant way possible.The method returns a primitive long.I've implemented this using both reflection and MethodHandles.I was expecting...
View ArticleMethodHandle cannot be cracked when using LambdaMetafactory?
I want to convert a Record's constructor to a Function<Object[], T> using lambdametafactory (T is a generic type), here are my codes:public record R( String a, String b) {}private static void...
View Article"Cannot cast [Ljava.lang.Object;" passing Object[] to Object... varargs
I'm struggling with a simple, fundamental Java language question that isn't making sense. I'm passing an Object[] to a method which expects varargs Object..., but the method seems to be interpreting...
View ArticleWrongMethodTypeException with MethodHandle.invokeExact() but no arguments and...
I'm using Java 17 on AWS Lambda. I have an interface Foo with a method bar(), returning a CompletableFuture<Map<Bar, Long>>:public interface Foo { public CompletableFuture<Map<Bar,...
View ArticleHow to get around IllegalAccessError when creating a MethodHandle from...
I am trying to get a MethodHandle for any of the constructors of the com.sun.tools.javac.code.TypeMetadata.Annotations record on JDK 21. Here is the source code of TypeMetadata (from...
View ArticleLambdaMetaFactory with Generic Static Methods?
So I'm creating a library that allows users to pass a Class<?> and collect all static methods with a specific annotation (and other criteria, such as a certain parameter count and types) and...
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