LECTURE NOTES
SEPTEMBER 27 2004

ASSIGNMENTS
10/1 Assignment 1 - Be sure to read style and commenting guides online: you will be graded on these!
     CodeLab 4

USING VISIBILITY MODIFIERS

Why?
- ensure class integrity
- avoid back doors that can break the functionality of the class
What?
- private data members
How?
- clients can only access data in ways you specifically enable

What?
- public class constants
Why?
- by nature can't be modified
- clean way to make certain characteristics of instances known to client programmers

What?
- using public class data members
How?
- <class name>.<class data member>

What?
- visibility modifiers and class diagrams
how?
- place symbol at beginning of each data member or method
- "+" for public
- "-" for private

VARIABLE SCOPE: USING ARGUMENTS, PARAMETERS, AND LOCAL VARIABLES

What?
- using data members within a class definition
How?
- refer to them by name

What?
- declaring *local variables*
Why?
- temporary purposes
- storing the intermediate result of a computation

What?
- parameter
  - variable input to a method
  - optional

What?
- accessibility of local variables and parameters
When?
- within the method in which they are declared
- available only when the method is being executed

What?
- memory usage of local variables and parameters
How?
- memory space
  - allocated at the beginning of the method
  - erased upon exiting from the method

What?
- passing arguments to a method
When?
- a method is called
How?
- value of argument stored in the parameter in the corresponding position
- *pass-by-value* / call-by-value
- parameter and argument names can be the same
Ramifications?
- changes made to the parameter do not affect the original argument
- data type of argument must be assignment-compatible with the data type of the parameter
Program Diagram Notation?
  <visibility symbol> <method name>(<list of parameter types>)

What?
- returning values from a method
How?
- data type of the return value must be assignment-compatible with the declared return type
- method call acts like an expression that evaluates to the method's return value
Ramifications?
- *method composition*
Program Diagram Notation?
  <visibility symbol> <method name>(<list of parameter types>) : <return type>

What?
- passing objects
How?
- pass by value
- data just happens to be the address of an object
Ramifications?
- object itself is shared, not copied

What?
- returning objects
How?
- make the return type the name of a class
Ramifications?
- method call evaluates to the address of the returned object

What?
- pass-by-reference: the address of a variable is passed as a parameter
- aka call-by-reference
How?
- not done in Java