How can the type of a bean property be null?

Question

In the book "Thinking in Java" there is an example of how to get information for a bean via Reflection/Introspection.

BeanInfo bi = Introspector.getBeanInfo(Car.class, Object.class);
for (PropertyDescriptor d: bi.getPropertyDescriptors()) {
  Class<?> p = d.getPropertyType();
  if (p == null) continue;
  [...]
}

In line 4 of that sample above there is a check if the PropertyType is null. When and under what circumstances does that happen? Can you give an example?

Answer 1

From the JavaDoc:

Returns null if the type is an indexed property that does not support non-indexed access.

So I guess if the property type is an indexed property(like an array) it will return null.