Java Reference
In-Depth Information
persthatareaccessiblefromOracle's“JavaHotSpotGarbageCollection”pageat
ht-
Chapter4
pursuesgarbagecollectionfurtherbyintroducingyoutoJava'sReference
API, which lets your application receive notifications when objects are about to be fi-
nalized or have been finalized.
Note
Throughoutthisbook,Ioftenreferto
API
inbothbroadandnarrowcontexts.
Ontheonehand,IrefertoReferenceasanAPI,butIalsorefertotheindividualclasses
of Reference as APIs themselves.
EXERCISES
The following exercises are designed to test your understanding of classes and ob-
jects:
method for testing this class. Expand
Image
by introducing private
int
fields named
width
and
height
, and a private one-dimensional byte
array field named
image
. Refactor the
Image()
constructor to invoke
the
Image(String filename)
constructorvia
this(null)
.Refact-
or the
Image(String filename, String imageType)
con-
structor such that, when the
filename
reference is not null, it creates a
byte array of arbitrary size, perhaps with the help of an expression such
as
(int) (Math.random()*100000)
(return a randomly generated
integer between 0 and 99999 inclusive), and assigns this array's reference
to the
image
field. Similarly, it assigns an arbitrary width to the
width
field and an arbitrary height to the
height
field. If
filename
contains
null, it assigns -1 to each of
width
and
height
. Continuing, introduce
getWidth()
,
getHeight()
, and
getImage()
methods that return
the values of their respective fields, and introduce a
getSize()
method
thatreturnsthelengthofthearrayassignedtothe
image
field(or0if
im-
age
containsthenullreference).Finally,refactorthe
main()
methodsuch
that, for each constructor, the following sequence of method calls occurs:
System.out.println("Image = "+image.getImage());
System.out.println("Size = "+image.getSize());
System.out.println("Width = "+image.getWidth());
System.out.println("Height = "+image.getHeight());
.
