Java Reference
In-Depth Information
The set
layouts
is expected to contain just one item because the number of compon-
ents for both the navigator and the widget being added is 1. However, the
getLayoutS-
ize()
method returns 2.
The reason for this discrepancy is that the
hashCode()
method of
Widget
is used only
once when the widget is added to the set. When the navigator is added, the
hashCode()
method provided by the
Navigator
class is used. Consequently, the set contains two dif-
ferent object instances.
Compliant Solution (
final
class)
Thiscompliantsolutiondeclaresthe
Widget
classfinalsothatitsmethodscannotbeover-
ridden:
public final class Widget {
// ...
}
Noncompliant Code Example (
run()
)
Inthisnoncompliantcodeexample,class
Worker
anditssubclass
SubWorker
eachcontain
a
startThread()
method intended to start a thread.
public class Worker implements Runnable {
Worker() { }
public void startThread(String name) {
new Thread(this, name).start();
}
@Override
public void run() {
System.out.println("Parent");
}
}
public class SubWorker extends Worker {
@Override
public void startThread(String name) {
super.startThread(name);
new Thread(this, name).start();
}
@Override
