Java Reflection getDeclaredMethod() with Generic Class Type

Question

I have a method in class A:

class Parameter {
...
}

class A {
   private <T extends B> void call(T object, Parameter... parameters){
   ...
   }
}

Now I want to use reflection to get the method "call",

A a = new A();
// My question is what should be arguments in getDeclaredMethod
//Method method = a.getClass().getDeclaredMethod()

Thx.

Class a = new A(); is not valid. You either mean Class a = new A().getClass(); or A a = new A();. — ApproachingDarknessFish
– ApproachingDarknessFish, Commented Aug 24, 2013 at 5:11

Paul Bellora · Accepted Answer · 2013-08-24 04:47:10Z

7

They should be B and Parameter[], since B is the erasure of T and varargs are implemented as arrays:

Method method = a.getClass().getDeclaredMethod(
        "call",
        B.class,
        Parameter[].class
);

Note that you have a syntax error: <T extends of B> should be <T extends B>.

Also note that the method as you're showing it doesn't need to be generic at all. This would work just as well:

private void call(B object, Parameter... parameters) { ... }

answered Aug 24, 2013 at 4:47

Paul Bellora

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2 Comments

user537555 Over a year ago

Thanks, It works! I also have updated the syntax error. Btw, I wonder why B.class works here and what Parameter[].class means.

Paul Bellora Over a year ago

@user537555 Glad to help! .class returns the Class literal representing that type. It works for array types like Parameter[].class and even primitive types like int.class (that's how you can look up a method taking an int).

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