Java Reference
In-Depth Information
b)
All generic method declarations have a type-parameter section that immediately pre-
cedes the method name.
c)
A generic method can be overloaded by another generic method with the same method
name but different method parameters.
d)
A type parameter can be declared only once in the type-parameter section but can ap-
pear more than once in the method's parameter list.
e)
Type-parameter names among different generic methods must be unique.
f)
The scope of a generic class's type parameter is the entire class except its
static
mem-
bers.
20.2
Fill in the blanks in each of the following:
a)
and enable you to specify, with
a single method declaration, a set of
related methods, or with a single class declaration, a set of related types, respectively.
b)
A type-parameter section is delimited by
.
c)
A generic method's can be used to specify the method's argument types, to
specify the method's return type and to declare variables within the method.
d)
The statement "
Stack
objectStack
=
new
Stack();
" indicates that
objectStack
stores
.
e)
In a generic class declaration, the class name is followed by a(n)
.
f)
The syntax
specifies that the upper bound of a wildcard is type
T
.
Answers to Self-Review Exercises
20.1
a) False. Generic and nongeneric methods can have the same method name. A generic
method can overload another generic method with the same method name but different method
parameters. A generic method also can be overloaded by providing nongeneric methods with the
same method name and number of arguments. b) False. All generic method declarations have a
type-parameter section that immediately precedes the method's return type. c) True. d) True.
e) False. Type-parameter names among different generic methods need not be unique. f) True.
20.2
a) Generic methods, generic classes. b) angle brackets (
<
and
>
). c) type parameters. d) a
raw type. e) type-parameter section. f)
?
extends
T
.
Exercises
20.3
(Explain Notation)
Explain the use of the following notation in a Java program:
public class
Array<T> { }
20.4
(Generic Method
selectionSort
)
Write a generic method
selectionSort
based on the
sort program of Fig. 19.4. Write a test program that inputs, sorts and outputs an
Integer
array and
a
Float
array. [
Hint:
Use
<T
extends
Comparable<T>>
in the type-parameter section for method
se-
lectionSort
,
so that you can use method
compareTo
to compare the objects of the type that
T
rep-
resents.]
20.5
(Overloaded Generic Method
printArray
)
Overload generic method
printArray
of
Fig. 20.3 so that it takes two additional integer arguments,
lowSubscript
and
highSubscript
. A call
to this method prints only the designated portion of the array. Validate
lowSubscript
and
highSub-
script
. If either is out of range, the overloaded
printArray
method should throw an
InvalidSub-
scriptException
; otherwise,
printArray
should return the number of elements printed. Then
modify
main
to exercise both versions of
printArray
on arrays
integerArray
,
doubleArray
and
characterArray
. Test all capabilities of both versions of
printArray
.
