methodhandle

Java's MethodHandle.invokeExact(Object...args) takes a variable-length list of arguments. When I try to pass an array of Object [] instead of a list, though, I get an error. See below: private void doIt() throws Throwable { Method meth = Foo.class.getDeclaredMethods()[0]; MethodHandles.Lookup lookup = MethodHandles.lookup(); MethodHandle mh = lookup.unreflect(meth); Foo foo = new Foo(); String myStr = "aaa"; Integer myInt = new Integer(10); Object [] myArray = {foo, myStr, myInt}; mh.invokeExact(foo, myStr, myInt); // prints "Called aaa 10" mh.invokeExact(myArray); // throws Exception } class

I wrote a little benchmark that tests performance of java.lang.invoke.MethodHandle , java.lang.reflect.Method and direct calls of methods. I read that MethodHandle.invoke() performance almost the same as direct calls. But my test results show another: MethodHandle invoke about three times slower than reflection. What is my problem? May be this is result of some JIT optimisations? public class Main { public static final int COUNT = 100000000; static TestInstance test = new TestInstance(); static void testInvokeDynamic() throws NoSuchMethodException, IllegalAccessException { int [] ar = new int

I have spend whole day on this problem. My problem is how to make an MethodHandle.invokeExact invocation on an instance, whose class type is dynamically loaded at program runtime. To make problem more clear, i show my sample code below: Class<?> expClass = new MyClassLoader().load(....) //expClass is AddSample.class which is subclass of BaseTemplate BaseTemplate obj = expClass.getConstructor(...) .newInstance(...); MethodHandle myMH = MethodHandles.lookup().findVirtual(expClass, methodName,..); System.out.println("Object type "+obj.getClass()); //Print AddSample // If obj is declared as

How can I invoke private method using method handles ? As far as I can see there are only two kinds of publicly accessible Lookup instances: MethodHandles.lookup() MethodHandles.publicLookup() and neither allows unrestricted private access. There is the non-public Lookup.IMPL_LOOKUP that does what I want. Is there some public way to obtain it (assuming that SecurityManager allows it) ? Turns out it's possible with Lookup#unreflect(Method) and temporarily making method accessible (potentially introducing small security issue unless done during program initialization). Here is modified main

Java 8 has introduced lambda expressions , which is a great thing. But now consider rewriting this code: class B implements PropertyChangeListener { void listenToA(A a) { a.addPropertyChangeListener(this); } void propertyChange(PropertyChangeEvent evt) { switch(evt.getPropertyName()) { case "Property1": doSomething(); break; case "Property2": doSomethingElse(); case "Property1": doSomething; break; break; } void doSomething() { } void doSomethingElse() { } } class A { final PropertyChangeSupport pcs = new PropertyChangeSupport(this); void addPropertyChangeListener(PropertyChangeListener