Java Reference
In-Depth Information
Self-Test Exercises
47. When run in default mode, does
javadoc
ever extract the body of a method
defi nition? When run in default mode, does
javadoc
ever extract anything
marked private in a class defi nition?
48. When run in default mode, what comments does
javadoc
extract and what
comments does it not extract?
Chapter Summary
•
A
static method
is one that does not require a calling object, but can use the class name
in place of the calling object.
•
A
static variable
is similar to an instance variable except that there is only one copy of
the static variable that is used by all objects of the class.
•
A
wrapper class
allows you to have a class object that corresponds to a value of a primi-
tive type. Wrapper classes also contain a number of useful predefined constants and
static methods.
•
A variable of a class type stores the reference (memory address) of where the object
is located in the computer's memory. This causes some operations, such as
=
and
==
,
to behave quite differently for variables of a class type than they do for variables of a
primitive type.
•
When you use the assignment operator with two variables of a class type, the two
variables become two names for the same object.
•
A method cannot change the value of a variable of a primitive type that is an argu-
ment to the method. On the other hand, a method can change the values of the
instance variables of an argument of a class type. This is because with class parameters,
it is a reference that is plugged in to the parameter.
•
null
is a special constant that can be used to give a value to any variable of any class type.
•
An expression with a
new
operator and a constructor can be used as an argument to
a method. Such an argument is called an
anonymous object
.
•
A
copy constructor
is a constructor with one parameter of the same type as the class.
A copy constructor should be designed so the object it creates is intuitively an exact
copy of its parameter, but is a completely independent copy—that is, a
deep copy
.
•
A class that contains mutator methods or any methods that can change the data in an
object of the class is called a
mutable class
, and objects of the class are called
mutable
objects
. When defining accessor methods (or almost any methods), your method
should not return a reference to a mutable object. Instead, use a copy constructor (or
other means) to return a reference to a deep copy of the mutable object.
