Final answer:
To maintain pre-generic compatibility in Java, type parameters are replaced by "raw types." Raw types act as if they have no generic type information, defaulting to Object, and allowing older, non-generic code to interact with generic code.
Step-by-step explanation:
To maintain compatibility with pre-generic Java, type parameters are replaced by ordinary types called raw types. Raw types allow older code written before generics were introduced to the language (in Java 5) to interoperate with generic code. They represent the raw form of a generic class or interface, effectively behaving as if all generic type information was erased and replaced with the most general type: Object. For instance, a generic class List<T> can be used as a raw type simply by referring to it as List without specifying a type parameter. However, using raw types is discouraged as it bypasses the type safety that generics provide.