如何用泛型返回类型推断方法的特定返回类型? [英] How to infer the specific return type of a method with a generic return type?

问题描述

给出以下界面:

interface Random extends java.util.function.Supplier<Integer> { }

带有 java.util.function.Supplier 的

看起来像这样(缩写):

with java.util.function.Supplier looking like this (abbreviated):

public interface Supplier<T> { T get(); }

现在考虑以下几点:

java.lang.reflect.Method get = Random.class.getMethod("get");
System.out.println(get.getReturnType()); // prints `class java.lang.Object`
System.out.println(get.getGenericReturnType()); // prints `T`

如何推断返回类型实际上应该是 java.lang.Integer ?

How can I infer that the return type should actually be java.lang.Integer?

推荐答案

您可能可以使用下面的代码执行此操作.这里的想法是通用类型信息可能在字节码中可用，并且可以在运行时访问.请参阅下面的链接以获取更多详细信息.

You can probably do this with something like below code. The idea here is that the generic type information is potentially available in the byte code and can be accessed at runtime. Refer the link below for more details.

ParameterizedType parameterizedType = (ParameterizedType) subClass.getGenericSuperclass();
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  return (Class<?>) parameterizedType.getActualTypeArguments()[parameterIndex];

https://www.javacodegeeks.com/2013/12/advanced-java-generics-retreiving-generic-type-arguments.html

在线上还有其他一些有用的文章对此进行了描述.

There are some other useful articles online which describe this too.

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