通过功能接口方法签名获取 class 构造函数

Question

I know i can use constructor reference as hihger-order method's argument like this:

collection.stream().map(MyClass::new);

But I have MyClass as a variable Class<MyClass> clazz = MyClass.class . Can I use it to pass constructor reference to .map(Function) method? I want to do something like this, is there a way to do it?

Class<MyClass> clazz = MyClass.class;
collection.stream().map(clazz.getConstructor())

Answer 1

Standard disclaimer: Use of reflection is almost always a bad idea.

It is much better to go for a standard Abstract Factory or similar.

However, MethodHandle will construct the required Function objct with minimal overhead (I think). If you do the lookup of fn every time, there is overhead in that.

    Function<T, R> fn = (Function<T, R>)
        MethodHandleProxies.asInterfaceInstance(
            Function.class,
            MethodHandles.lookup().findConstructor(clazz,
               MethodType.methodType(Void.TYPE, tClass)
           )
        );

Exception handling elided.