Object-oriented Programming

Object-oriented Programming

1. Classes: template to create identical types of objects

   • Objects: living, non-living, abstract, or concrete
     • Attributes = fields
       • Capitalize the initial of each word except the first one
     • Actions = methods
       • Capitalize the initial of each word except the first one
       • returnType methodName (liistOfArguments)
         • Ex: double getSalary ()
           • Ex: int add (int a, int b)
     • use a period to call a method or field
       • objectReference.methodName
         • objectReference.fieldName
       • see note for example code
         • Employee employee = new Employee () employee.age = 24 employee.salary = 50000
   • class className { [class body] }
     • class body contains fields and attributes
     • Capitalize initial of each word of each class name

2. The Method Main

   • Entry point into the application. Only one class needs it
   • Passing arguments to main: java className arg1 arg2 arg3
     • Must pass arguments as strings

3. Constructors: every class needs at least one

   • Similar to a method but without a return value
   • Must have same name as class
   • constructorName (listOfArguments) { [constructor body] }
   • One is assigned if you don't write one

4. Creating Objects

   • 'New' command
     • new Employee ()
       • Employee employee = new Employee ()