Java Reference
In-Depth Information
C H A P T E R 2
Discovering Classes and Objects
Chapter1
gentlyintroducedyoutotheJavalanguagebyfocusingmainlyonfundamental
languagefeaturesrangingfromcommentstostatements.Usingonlythesefeatures,you
cancreatesimpleapplications(suchas
HelloWorld
andtheapplicationsmentionedin
thechapter'sexercises)thatarereminiscent ofthosewritteninstructuredprogramming
languages such as C.
Note
Structured programming
is a programming paradigm that enforces a logical
structure on programs through
data structures
(named aggregates of data items),
func-
tions
(named blocks of code that return values to the code that calls [passes program
execution to] them), and
procedures
(named blocks of code that don't return values
to their callers). Structured programs use sequence (one statement follows another
statement),selection/choice(if/switch),andrepetition/iteration(for/while/do)program-
ming constructs; use of the potentially harmful GOTO statement (see
ht-
tp://en.wikipedia.org/wiki/GOTO
) is discouraged.
Structured programs separate data from behaviors. This separation makes it difficult
tomodelreal-worldentities(suchasabankaccountsandemployees)andoftenleadsto
maintenanceheadacheswhenprogramsbecomecomplex.Incontrast,classesandobjects
combinedataandbehaviorsintoprogramentities;programsbasedonclassesandobjects
are typically easier to understand and maintain.
Chapter2
takesyoudeeperintotheJavalanguagebyfocusingonitssupportforclasses
andobjects.Youfirstlearnhowtodeclareclassesandcreateobjectsfromtheseclasses,
andthenlearnhowtoencapsulatestateandbehaviorsintotheseprogramentitiesthrough
fields and methods. After learning about class and object initialization, you move bey-
ond this
object-based programming
model and dive into
object-oriented programming
,
by exploring Java's inheritance- and polymorphism-oriented language features.
