Generics are used for tighter type checks at compile time and to provide a generic programming. To implement generic behaviour, java compiler apply type erasure. Type erasure is a process in which compiler replaces a generic parameter with actual class or bridge method. In type erasure, compiler ensures that no extra classes are created and there is no runtime overhead.
Replace type parameters in generic type with their bound if bounded type parameters are used.
Replace type parameters in generic type with Object if unbounded type parameters are used.
Insert type casts to preserve type safety.
Generate bridge methods to keep polymorphism in extended generic types.