For example, let's get the generic return types for the slice() and asMap() methods. This can be accomplished via the Method.getGenericReturnType() method as follows:

Class<Melon> clazz = Melon.class;

Method sliceMethod = clazz.getDeclaredMethod("slice");
Method asMapMethod = clazz.getDeclaredMethod("asMap", List.class);

Type sliceReturnType = sliceMethod.getGenericReturnType();
Type asMapReturnType = asMapMethod.getGenericReturnType();

Now, calling printGenerics(sliceReturnType) will output the following:

Class of type argument: class modern.challenge.Slice
Simple name of type argument: Slice

And, calling printGenerics(asMapReturnType) will output the following:

Class of type argument: class java.lang.String
Simple name of type argument: String

Class of type argument: class java.lang.Integer
Simple name of type argument: Integer

Generic parameters of methods can be obtained via Method.getGenericParameterTypes(), as follows:

Type[] asMapParamTypes = asMapMethod.getGenericParameterTypes();

Further, we call printGenerics() for each Type (each generic parameter):

for (Type paramType: asMapParamTypes) {
  printGenerics(paramType);
}

Following is the output (there is a single generic parameter, List<Melon>):

Class of type argument: class modern.challenge.Melon
Simple name of type argument: Melon