Chapter 7 is about generics, which are templated collections. Generics improve upon non-generic collections. Generics improve performance mostly by eliminating boxing. They are bound to specific types at compile time. Non-generic collections rely on object types. When populating non-generic collections with values, boxing occurs because of casting from a value type to a reference type. Excessive boxing incurs both a performance and a memory penalty. Boxing also causes problems with type safety. You often cast elements that are object types to a specific type. The cast is not type-safe and can cause runtime errors when done incorrectly. Because generics are type-specific, the need for a cast is eliminated.

Generic types are classes with type parameters. The type parameter acts as a placeholder for a future type. When a generic type is declared, type arguments are substituted for the type parameters. At that time, the generic becomes type-specific, thus resolving many of the problems inherent in non-generic collection types. Generic methods, like generic types, have type parameters. However, the type argument can be inferred from the way the method is called.