Java Trivia Point 6

Code written with a generic mechanism has better security and readability in code that enforces type conversions than those that are cluttered with variables that use the type object.

Generic class:

The type variable t is placed after the class name, with <>, and the generic class can be regarded as the factory of the ordinary class.

Generic methods:

The generic is placed after the modifier and returns the front of the type.

Qualification of generic type variables:

Whether a generic type is defined appropriately, a corresponding primitive type erase type variable is automatically supplied, replaced with a qualified type (No limit to object)

The compiler automatically inserts force type catch.

Constraints:

• You cannot instantiate a generic parameter with a base type
• Run-time type queries apply only to the original type (a instanceof pair<string>, false)
• Cannot create an array of parameterized types
• Cannot instantiate type variable (new T ())
• Cannot reference a type variable in a static field or method
• An instance of a generic class cannot be thrown or captured

Two classes have an inheritance relationship, the generic class is not connected

Wild-Letter wildcard types:

Wildcard characters can also specify a super-type qualification:? Super Manager

Wildcard characters with a super-type qualification can be written to generic objects, and wildcard characters with sub-type qualification can be read from generic types.

Java Trivia Point 6