Kamila Jolan

Hi Hebert

I managed to get this working. I had forgot to create the JNDI entries for the JMS resource in Glassfish. Thanks for your help.

Hebert, thanks for answer, I still tried that but I still have that error.

Hi,

I got the application that works correctly on Glassfish V2, however when I try to migrate it to Glassfish V3 i have following exception:

javax.naming.CommunicationException: Can't find SerialContextProvider [Root exception is java.lang.ClassCastException]
at com.sun.enterprise.naming.SerialContext.getProvider(SerialContext.java:164)
at com.sun.enterprise.naming.SerialContext.lookup(SerialContext.java:409)
at javax.naming.InitialContext.lookup(InitialContext.java:409)
at com.jmwrti.timetableserver.TimetableHandler.getTimetableImportDAO(TimetableHandler.java:66)
Caused by: java.lang.ClassCastException
at com.sun.corba.ee.impl.javax.rmi.PortableRemoteObject.narrow(PortableRemoteObject.java:258)
at javax.rmi.PortableRemoteObject.narrow(PortableRemoteObject.java:153)
at com.sun.enterprise.naming.SerialContext.narrowProvider(SerialContext.java:136)
at com.sun.enterprise.naming.SerialContext.getCachedProvider(SerialContext.java:259)
at com.sun.enterprise.naming.SerialContext.getRemoteProvider(SerialContext.java:204
Caused by: java.lang.ClassCastException: Object is not of remote type com.sun.enterprise.naming.SerialContextProvider
at com.sun.corba.ee.impl.javax.rmi.PortableRemoteObject.narrow(PortableRemoteObject.java:250)

Here is the method that do the lookup:
private final static String SESSION_IMPORT = "com.jmwrti.session.timetableimport.TimetableImportRemote"; /** Looks up a timetable import session bean on the server. * @return the timetable import bean */ private TimetableImportRemote getTimetableImportDAO(Context jndiContext) { try { Object ref = jndiContext.lookup(SESSION_IMPORT); return (TimetableImportRemote)PortableRemoteObject. narrow(ref,TimetableImportRemote.class); } catch (NamingException ex) { ex.printStackTrace(); } return null; }

Here is the the interface:
@Remote public interface TimetableImportRemote extends TimetableImportBase { //some methods here }
The bean:
@Stateless public class TimetableImportBean implements TimetableImportLocal, TimetableImportRemote { ..//some code here.}

I really dont understand why this is not working on Glassfish V3. I tried to remove the narrow method but the exception is still appearing. I am newbe to Glassfish and EJB so any help would be appreciated.

Thanks,
Kamila

Stephan thanks for explanation I think i almost got it ,
but then why if I wrote that code:
int [] arr =new int [10]; arr[--k] += k = 4 * k + 2;
the value 2 is inserted in the position 0 in the array, I would say that this is happening:
arr[--k] =arr[--k] + (k = (4 * k) + 2); arr[--1] =arr[--1] + (k = (4 * 1) + 2); arr[0]=arr[0] +(k = 6); arr[0]=0+6 ->6

but the value is 2 not 6
Thanks

Hello,

Could you please elaborate more why after k += k = 6; the left-most k still has the original value as 1 ? I thought that after assignment k = 6 it would change the value to 6 so it will be 6+6 not 1+6.

Thanks.

Hello,

I was wondering is it required to know how the overriding/overloading works in generic classes for SCJP exam? I found examples here but this topic is not really covered in the K&B book, so I am confused.

Kindest regards,
Kamila

Hello,

I know that it is not possible to create an object with a generic type like this:
T ref = new T();
It is also wrong to create generic array like:
T[] arrayRef = new T[10];
then can somebody please explain me why it is possible to create an list like that(assuming that this code is in the generic class ):
List<T>[] arrayOfLists = new List<T>[10];
but not for example an array of lists:
List<T>[] arrayOfLists = new ArrayList<T>[10]; but then if i use a wildcard this works:
List<?>[] arrayOfLists = new List<?>[10];


Any help will be appreciated.

regards,

Kamila

Hello,

The following code is from examlab. I dont understand why the IterruptedException is not appearing. I noticed that the wait() method is not within the synchronized context so the IllegalMonitorStateException should be thrown, but why IterruptedException is not appearing before that? It seems that method a.interrupt(); does not cause any effect here.

public class Watek extends Thread{ public static void doDelay(long t){ try{ Thread.sleep(t); }catch(InterruptedException e){ System.out.print("Ex-A "); } } public void run(){ doDelay(1000); halt(); } public void halt(){ try{ this.wait(); }catch(Exception e){ System.out.print("Ex-B "); } } public static void main()throws Exception{ Watek a=new Watek(); Thread t=new Thread(a); t.start(); doDelay(100); a.interrupt(); doDelay(2000); t.notifyAll(); } }


From the output I get I think that after method main is started the main thread is delayed in the doDelay() method and then thread t is started and delayed as well. Next the main thread wakes up and returns from main doDelay() method but it is being delayed again for at least 2000 milisec. Finally, the thread t wakes up and invokes halt() method but because the wait() is not within the synchronized context the IllegalMonitorStateException is thrown.
Why the interrupt() method does not have any effect here? I thought that when the main thread returns from the doDelay() method and invokes interrupt() while the thread t is still "sleeping" the IterruptedException should be thrown because thread t should be interupted??

Thanks

Thanks a lot

Hello,

Can somebody help me understand why this code:


class Parent { String s= "Parent"; void someMethod() { System.out.println(s); } void show() { someMethod(); System.out.println(s); } } class Child extends Parent { String s= "Child"; void someMethod() { System.out.println(s); } } public class Test { public static void main(String[] args) { Parent parent = new Child(); parent. show() ; //or new Child ().show (); } }

giving the following results :
Child
Parent
I understand why the "Child" is appearing - the overridden method "someMethod()" will be invoked and it will use the "s" variable from the Child class. That is why I don't know why the show() method will use the "s" variable from the Parent class in the second case (line 9). The Child object is created and the show() method is inherited by the Child class.

Any help will be appreciated

Thanks a lot for help! now I got it

Swaraj thanks for the answer, I know that "==" and "!=" preform automatic boxing, but I am not sure what "<" and ">" doing with the wrappers?

Hello,

I would like to ask why the following code works:

Short s1= 1; if(s1 < new Integer(7+1)) ...

If we use the "==" or "!=" instead of "<" or ">" the code won't compile because two different wrapper type cannot be compared. Are the operators like "<" or ">" preform an automatic cast like compound assignments(e.g. +=)??


Kindest regards,

Kamila

Thank you very much for reply.

Could you elaborate more why then there are two "" characters at the beginning and none at the end of the result?

Regards,
kamila

Hi,

I have a problem with understanding the String split() method. I read the documentation but I cannot figure it out how this is

accualy working. If I use this code:

String source= "abab"; String []stab=s.split("b");

the result is:["a","a"]. Thus, I thought that this method splits the string removing delimiter.

Although when I run the follwing code:
String source= "bbababbaabbabb"; String []stab=s.split("b");

The result is:["","","a","a","","aa","","a"]
..........index: 0 ..1 ..2 ...3 ..4 ...5 . 6 . 7

I dont understand why at the beggining of the output(index 0 and 1) as well as on index 4 when two "bb" letter were, the character "" appeared. It seems like those "bb"characters were replaced by "" but then why at the end of the result the "" is not appiring?The source string has to "bb" at the end as well.

I will be greatfull if somebody could explain me this.

Regards,

Kamila