Pre-Finals

• Enumeration (enum)


  A data type that contains a fixed set of constants
• Enums are good to use when you already know all possibilities of the values or instances of the class
• With enums, it is impossible to create an invalid enum value without introducing a compiler error
• Examples of when enumerations are used

  • Compass directions
  • Months of the year
  • Cards in a deck
• Creating an enum


  1. Declare a type with the enum keyword

  2. Identifier for the type

  3. List of values called enum constants
• Enum constants


  • The only allowed values for the type
• Enum type


  A class, with enum constants acting like objects instantiated from the class
• Built-in enum methods


  • toString()
  • ordinal()
  • equals()
  • compareTo()
• valueOf()


  Accepts a string parameter and returns an enumeration constant
• values()


  Returns an array of the enumerated constants
• Declaring an enum


  In its own file or within a class but not within a method
• Enum usage


  • Selecting a grading period
  • Controlling a switch structure
• Type-safe


  Allows only appropriate behaviors
• Nested class


  A class created within another class
• Types of nested classes

  • Static member class
  • Non-static member class (inner class)
  • Local class
  • Anonymous class
• Reason for nesting a class

  • The inner class is used only by the top-level class
• Nested class example


  • RealEstateListing class with HouseData inner class
• An inner class can access its top-level class's fields and methods, even if they are private
• An outer class can access its inner class's members
• You usually will not want to create inner classes, as they are only usable in the class they reside in