CS115 lecture notes, Spring 1999
Week 7, Wednesday

EXAM FRIDAY:  Chapters 1-6 and up to 7.4

All lecture notes, labs and quizzes are also fair game.


Continuation of charAt discussion...

index
-----

An index is a value or variable that is used to "indicate"
one of the elements of a set.

In this case the set is the letters in the String.

All indixes are integers.

An index is one of the "roles" a variable plays
(along with loop variable, lower and upper bound,
counter and accumulator).


Traversing a String
-------------------

Write a loop that reads the characters of a String one at
a time and prints them.  Section 7.3


Break: throw snowballs at passersby.


EXAM REVIEW:  mechanism and abstraction


mechanism		    abstraction
---------		    -----------

method implementation	    method documentation
(body)			    what it does
how it works		    what parameters/return value

method invocation	    method invocation
mechanism		    (high-level view)

follow the stack	    leap of faith

iteration tables	    abstract loop constructs
			    traversal
			    loop variable "goes from a to b"
			    indices


Everything in the left column is important to know so
that you are aware of how things work.

Also, you can _start_ by understanding the mechanism.

Eventually, you need to shift your attention to the
right.

When you read programs, read them abstractly.  If nothing
else, it lets you read them more quickly.

When you write programs, think in terms of 

     abstract problem-solving building-blocks

Can you solve the problem by

1) writing a recursive definition and translating it into
   a recursive Java program?

2) traversing something and counting the number of times
   something happens?

3) traversing something and accumulating a result?


Final thoughts
--------------

why do methods exist?

parameters are hypothetical -- when you write the method
you don't know what they are

you have to write something general, that can deal with
any parameter values

when you invoke the method, that's when the parameters
get values.


FOUR KINDS OF METHODS
---------------------

1) void, fruitful

      (when you invoke a fruitful method, don't forget to
       do something with the result)

2) methods you invoke on objects, methods you just invoke.

   g.drawOval, System.out.println ...  factorial, paintShirt