Chap 3

Chap 3

1. Access Modifiers

   • public
     • everybody
   • used for classes, methods, and attributes
   • private
     • within the class
   • default
     • within class + package
   • protected
     • with class + package + subclass

2. methods

   • declaration
     • access modifier + static + return type + (parameters)
   • main
     • always automatically called by JVM
   • static
     • can be used without an object of the class which the method is declared
   • parameter vs argument
     • paramenter is the expected type specified
     • argument is the value passed to the method
   • has local variables
     • are not initialised by default
   • constructor
     • every time an object is created the constructor is called
     • has the same name of the class
     • default construtor is provided by the compiler with no parameter if there is no constructor declared in the code
     • It cannot return values

3. class

   • characteristics
     • java is an extensible language because you create a new type creating new class
     • any class can have a main method
     • classes in the same directory of the disk are implicitly imported
   • attributes
     • are initialised by default with zero or null

4. types

   • primitive types
     • int
     • float
       • floating-point numbers with 7 significant digits
     • double
       • floating-point numbers with 15 significant digits
     • char
     • byte
     • short
     • long
     • boolean
   • reference types
     • variables that store the location of objects