I have a method with parameter Function<Entity, Integer>. I pass a static method reference to that parameter Entity::getId.
Is it possible to, during runtime, extract the return class Class<Integer> from the function object?
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user2914191
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1What is your usecase? Why you need the return class `Class
` from the function object? – Ravindra Ranwala Oct 12 '18 at 05:16 -
the return type is generic. i dont know which type it is during runtime without passing a `Class
` around – user2914191 Oct 12 '18 at 05:22 -
1Show me how you call it. Your client side code which uses this `Class
`? – Ravindra Ranwala Oct 12 '18 at 05:23 -
come think of it, i think i can avoid the need for `Class`. but still an interesting question – user2914191 Oct 12 '18 at 05:29
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1You should be able to get rid of the `Class
` literal. If you can show me the usage I will be able to help. – Ravindra Ranwala Oct 12 '18 at 05:33 -
1These generic types are primarily intended for compile time. They are not available at runtime because of type erasure. https://stackoverflow.com/questions/313584/what-is-the-concept-of-erasure-in-generics-in-java – Thilo Oct 12 '18 at 06:00
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as GenericDeclaration says:
getTypeParameters() Returns an array of TypeVariable objects that represent the type variables declared by the generic declaration represented by this GenericDeclaration object, in declaration order.
so supposing you have your class declared as:
public class YourParametizedClass<Entity, Integer> {
...
}
then you would get the value of the second parameter by doing:
YourParametizedClass function=new YourParametizedClass();
function.getClass().getTypeParameters()[1].getName();
this will return you "Integer".
vmrvictor
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wouldnt it be `Function
func = Entity::getId` and then get type parameters of that object? – user2914191 Oct 12 '18 at 05:30 -
well it depends if the class already is defined as YourParametizedClass
then it would work – vmrvictor Oct 12 '18 at 05:33