Class

Class

1. Blueprint for an Object

   • Object (requires class)
     • Living
       • Persons
       • Pets
     • Not-living
       • Cars
       • Houses
     • Concrete
       • Books
       • Television
     • Abstract
       • Love
       • Knowledge
       • Tax Rate
     • Creating Objects (instance)
       • Create=Construct=Instantiate
       • to create an Employee object
         • new Employee ();

2. Needs Methods

   • Define actions that a class's objects can do
     • Method Main
       • Provides entry point to an application
       • signature of main
         • public static void main(String[] args)
       • Passing an argument to main
         • java className arg1 arg2 arg3 ...
         • arguments passed as Strings
           • java Test 1 safeMode
   • declaring a method:
     • returnType methodName (listOfArguments)
       • Return Type
         • primitive
         • object
         • null
     • If method takes more than one argument, arguments separated by comma
       • int add (int a, int b)
   • method that returns an address object
     • Address getAddress
   • method that accepts an argument
     • int negate(int number)

3. Class definition saved same name as class name

4. Has fields

   • age
   • maxAge
   • address
   • validAddress
   • numberOfRows

5. Constructors (all classes must have them

   • constructorName (listOfArguments) ( [Constructor body]
   • arguments used to initialize fields

6. Null Keyword

   • If a reference doesn't have a value, it has a null value
     • Book book // book is null
   • If object is not assigned:
     • Book book = null