Hi,
On 11 Mrz., 07:15, hyde <[email protected]> wrote:
> Hi all,
>
> building my homework work fine but when running the program I get the
> following errors:
>
> run:
> Exception in thread "main" java.lang.NullPointerException
> at MyOwnEvent.getCurrentTime(MyOwnEvent.java:20)
Here you see, that on line 20 of MyOwnEvent.java you get the error.
> at MyOwnListenerImpl.somethingHappened(MyOwnListenerImpl.java:
> 4)
> at MyOwnEventSource.triggerSomethingEvent
> (MyOwnEventSource.java:31)
> at MyOwnEventExample.main(MyOwnEventExample.java:12)
> Java Result: 1
> BUILD SUCCESSFUL (total time: 0 seconds)
>
> I´ m a little bit confused about how to return the date and time. I
> think there lies the root problem that leads to these errrors. Here´s
> a glance at my "MyOwnEvent.java":
>
> [...]
>
> import java.util.EventObject;
> import java.util.Date;
>
> public class MyOwnEvent extends EventObject {
>
> /** Creates a new instance of MyEvent */
> public MyOwnEvent(Object source) {
> super(source);
> }
>
> public MyOwnEvent(Object source, String myOwnEventName) {
> super(source);
> this.myOwnEventName = myOwnEventName;
> }
>
> private String myOwnEventName;
> private Date myOwnEventDate;
>
> public long getCurrentTime() {
> return myOwnEventDate.getTime();
myOwnEventDate is defined as a private field in your class.
The following method setMyOwnEventDate is under comment, so it
can't be called to set the myOwnEventDate, so the variable is null.
In getCurrentTime() you try to call the method getTime on
myOwnEventDate, which
does not reference to a valid object.
> }
>
> // public void setMyOwnEventDate(Date myOwnEventDate) {
> // this.myOwnEventDate = myOwnEventDate;
> // }
>
> }
>
> I always get in trouble with the myOwnEventDate variable. Does it
> really have to by a Date ? When using the myOwnEventDate within
> getCurrentTime it´s only possible to use "getTime". That´s why I
> declared the returning value of getCurrentTime as "long". Something´s
You can also use a Date object as return. The caller receives the
reference to the
object and the garbage collector does not recycle it.
HTH
Ewald
--~--~---------~--~----~------------~-------~--~----~
To post to this group, send email to [email protected]
To unsubscribe from this group, send email to
[email protected]
For more options, visit this group at
http://groups.google.com/group/javaprogrammingwithpassion?hl=en
-~----------~----~----~----~------~----~------~--~---
