Chapter 4

• A class is the blueprint for an object, it determine what the object knows (instance variables) and what the object does (methods).
• Instances in one class all have the same methods but the methods can 'behave' differently based on the values of the instance variables.
• You can send things to methods.
• You can use methods to return things.  (must declare a return type to get something back(returned))
• Methods can return "void".
• You can make things public or private.
• Use brackets ([#]) to get a number of things ( a certain number of objects in an array, or the number of times the dog will bark).
• Instance Variables have a defult value, local variables do not(method parameters act as local variables).

Variable           Default value

 



Integers                     0         

Floating Points             0.0                      
 
Booleans                 false                 
 
References                null                   
 
• Instance variables are declared inside a class but not within a method.
• Local variables are declared inside a method.
• Since local variables do not have a default value the must be initialized (given a value or defined) before you can run the program (but they can be placed/declared before being initialized).
• To test if primitives are the same use == .
• To test if objects are the same use .equals () .