Java generics and class literals

When using Mockito's ArgumentCaptor with a parameterized type like List<Long>, you run into a fundamental Java limitation: class literals for generic types don't exist (e.g., List<Long>.class is not valid syntax).

The Problem

The intuitive casting approach fails at compile time:

ArgumentCaptor<List<Long>> captor =
    (ArgumentCaptor<List<Long>>) ArgumentCaptor.forClass(List.class);
// Error: "Cannot cast from ArgumentCaptor<List> to ArgumentCaptor<List<Long>>"

The Solution

The working solution uses a double cast to bypass type safety restrictions:

ArgumentCaptor<List<Long>> captor =
    ArgumentCaptor.forClass((Class<List<Long>>)(Class) List.class);

This generates an unchecked type-safety warning but compiles and works correctly. The double cast first erases the raw type to Class, then casts it to Class<List<Long>>, which the compiler allows.

Alternative: @Captor Annotation

If you are using Mockito's annotation runner, the @Captor annotation avoids the casting entirely:

@Captor
private ArgumentCaptor<List<Long>> captor;

This approach is cleaner and avoids the type-safety warning, making it the preferred solution when using MockitoJUnitRunner or MockitoAnnotations.initMocks(this).