Java Reference
In-Depth Information
return rs.next();
}
}
Listing 9-20
refactors
Listing 9-17
by introducing a
boolean isEx-
ist(Connection con, String tableName)
class method, which returns
true when
tableName
exists, and using this method to determine the existence of
EMPLOYEES
before creating this table.
Whenthespecifiedtableexists,a
ResultSet
objectcontainingonerowisreturned,
and
ResultSet
's
next()
methodreturnstrue.Otherwise,theresultsetcontainsno
rows and
next()
returns false.
Caution
isExist()
assumes the default
APP
schema, which might not be the
casewhenusernamesareinvolved(eachuser'sdatabaseobjectsarestoredinaschema
corresponding to the user's name).
The Planets
Although helpful, the previous JDBC applications fall short in revealing the power of
JDBC,especiallywhencombinedwithSwing.Forthisreason,I'vecreatedamoreex-
tensive application named
Planets
that gives you an opportunity to explore these
APIsinamoreusefulcontext.Additionally,you'lldiscoversomethingnewabouteach
API.
The
Planets
application helps its user learn about the solar system's planets by
presentingimagesoftheeightplanetsalongwiththeirnamesandstatisticsontheirdia-
meters(inkilometers),masses(inkilograms),anddistancesfromtheSun(measuredin
astronomical units, or AUs, where Earth is 1 AU from the Sun).
I'vedesigned
Planets
torunintwomodes.Whenyouexecute
java Planets
initdb
, this application creates a
planets
database, populates its
PLANETS
table
witheightentries(whereeachentryrecordsa
String
-basedname,a
double
diamet-
er, a
double
mass, a
double
distance, and a
javax.swing.ImageIcon
object
storingtheplanet'simage),andthenterminates.Whenyouexecute
java Planets
,
this table's content is loaded, and then you see the GUI shown in
Figure 9-5
.
