7

CHAPTER

you saw how to create an object-oriented design through
the use of CRC cards and how to translate a CRC card description into a
Java class. At that time, we pointed out that classes can be related to each
other through a hierarchy of properties. The relationship between de-
rived classes (subclasses) and their superclass is defined by Java’s rules
of inheritance, which tell us the parts of the superclass that are auto-
matically included in the derived classes. Java also provides a set of rules
that determine the fields and methods of a class that can be accessed by
derived classes, classes in the same package, user code, and so on. We ex-
amine these rules in this chapter.
Also in this chapter, we describe a class within the input/output hi-
erarchy that allows us to write and read objects as a whole rather than
having to read them field by field.

In Chapter 6,

1964

Control Data

Corporation

presents Seymour

Cray’s CDC 6600,

the first commercial

supercomputer

1964

IBM develops a

computer-aided

design (CAD)

system

1964

Douglas Engelbart

invents the

computer mouse

1965

J.A. Robinson sets

the stage for logic

programming with

the development of

unification

1967

Ole-Johan Dahl and

Kristen Nygaard

create Simula, the

first object-oriented

programming

language

1967

The first hand-held

electronic calculator

that can add,

subtract, multiply,

and divide is created

by Jack Kilby, Jerry

Merryman, and

James Van Tassel at

Texas Instruments