java

1. Chapter 4
Writing Classes
– Part 1
Java Software Solutions
Foundations of Program Design
9th Edition
John Lewis
William Loftus

2. Key Concept
• The heart of object-oriented
programming is defining
classes that represent
objects with well-defined
state and behavior.

3. Key Concept
• The scope of a variable,
which determines where it
can be referenced, depends
on where it is declared.

4. Key Concept
• A UML class diagram helps
us visualize the contents of
and relationships among the
classes of a program.

5. Key Concept
An object should be
encapsulated, guarding its data
from inappropriate access.

6. Key Concept
Instance variables should be
declared with private visibility
to promote encapsulation.

7. Key Concept
• Most objects contain
accessor and mutator
methods to allow the client
to manage data in a
controlled manner.

8. Key Concept
The value returned from a
method must be consistent
with the return type in the
method header.

9. Key Concept
When a method is called, the
actual parameters are copied
into the formal parameters.

10. Key Concept
A variable declared in a
method is local to that method
and cannot be used outside of
it.

11. Key Concept
A constructor cannot have any
return type, even void.

12. Writing
Classes
• We've been using predefined classes from
the Java API. Now we will learn to write our
own classes.
• Chapter 4 focuses on:
• class definitions
• instance data
• encapsulation and Java modifiers
• method declaration and parameter passing
• constructors