Chapter 18, Problem 10RE

Program Plan Intro

Type Parameters:

• Type parameters are naming conventions and are important in java generic.
• The type parameters are used to keep the type safety especially when using the java collections like, “ArrayList”, “HashMap” and so on.
  • For example, the array list is not restricted to accept any particular set of data. So, it accepts any kind of data in it, even though the user is not indented to give these kinds of values.
  • So, it needs to be controlled and the type parameters help to keep the type safety of block of code.
  • The type parameters are the names like, “K”, “E” are given at the time of declaring the class or methods, then at the time of defining, the type of these parameters are specified clearly.
• The common type parameters are,
  • “T”-Type
  • “E”-Element
  • “K”-Key
  • “N”-Number
  • “V”-Value
• Each type parameter has their own purpose like, the type “K” is used represent some keys and the type “N” is used to represent some numbers.
• The type parameters can be used as the arguments of a method, return type of a method, type of class and so on.
• For a generic class or method, the user can give different combinations of type parameters as”<K, N>”.
• Then the user need to specify what is the type of this type parameters specifically when defining class members like, “ArrayList”, “HashMap” and so on.

Generic class:

• It is a class in which the class name is followed by the type parameter section.
• In generic class, one or more type arguments are separated by commas.
• The programmers are enabled to specify a single class declaration with a set of related type.