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Index ‹ java-programmer
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- 1
- Why does JMenuItem react to right button?In all the applications that I know, menu items react only to mouse
left-click. Swing JMenuItem, however, reacts to any mouse button click.
Swing JButton (which also extends AbstractButton) behaves as expected.
Does anybody know why? Is there any way to change this behavior?
Thanks in advance,
Diego
- 1
- newbie: "reference to object is ambiguous" errorHi!
I have this error compilling my application that I have created with
netbeans:
JFrameSample.java:164: reference to Object is ambiguous, both class
org.omg.CORBA.Object in org.omg.CORBA and class java.lang.Object
in java.lang match
new Object [][] {
^
1 error
How can I fix it? I need both: org.omg.CORBA and java.lang.*
any ideas?
Thanks!
LaCo
- 1
- FTPClient and CopyStreamAdapter stop sometimesI have an applet which Downloads some files from an FTP(S) Server.
Mostly everything works fine, but sometimes the application "stops"
for a long time (several minutes) after the "RETR filename" command.
PErhaps someone knows this problem or has an idea.
Thank you in advance for any hint,
Susanne
Here is some of my code:
try {
InputStream stO =
new BufferedInputStream(
ftps.retrieveFileStream(fileName),
ftps.getBufferSize());
org.apache.commons.net.io.Util.copyStream(
stO,
fout,
ftps.getBufferSize(),
//
org.apache.commons.net.io.CopyStreamEvent.UNKNOWN_STREAM_SIZE,
length,
new org.apache.commons.net.io.CopyStreamAdapter() {
public void bytesTransferred(long
totalBytesTransferred,
int bytesTransferred,
long streamSize) {
changeSupport.firePropertyChange(FTPPERCENT, null,
totalBytesTransferred*100/length);
}
});
} catch (Exception e) {
e.printStackTrace();
}
- 3
- [ANNOUNCEMENT]:VTD-XML released under GPL I am pleased to announce that version 0.5 of VTD-XML -- a new,
non-extractive, Java-base XML processing API licensed under GPL
-- is now freely available on sourceforge.net. For source code,
documentation, detailed description of API and code examples,
please visit
http://vtd-xml.sf.net
Capable of random-access, VTD-XML attempts to be both memory
efficient and high performance. The starting point of this project is
the observation that, for XML documents that don't declare entities
in DTD, tokenization can indeed be done by only recording the starting
offset and length of a token. A discussion on this subject appeared
in a recently article on xml.com
(http://www.xml.com/pub/a/2004/05/19/parsing.html).
The core technology of VTD-XML is a binary format specification
called Virtual Token Descriptor (VTD). A VTD record is a 64-bit integer
that encodes the starting offset, length, type and nesting depth of a
token in an XML document. Because VTD records don't contain actually
token content, they work alongside of the original XML document, which
is maintained intact in memory by the processing model.
VTD's memory-conserving features can be summarized as follows:
* Avoid Per-object overhead -- In many VM-based object-oriented
programming languages, per-object allocation incurs a small amount
of memory overhead. A VTD record is immune to the overhead because
it is not an object.
* Bulk-allocation of storage -- Fixed in length, VTD records can be
stored in large memory blocks, which are more efficient to allocate
and GC. By allocating a large array for 4096 VTD records, one incurs
the per-array overhead (16 bytes in JDK 1.4) only once across 4096
records, thus reducing per-record overhead to very little.
Our benchmark indicates that VTD-XML processes XML at the performance
level similar to (and often better than) SAX with NULL content handler.
The memory usage is typically between 1.3x ~ 1.6x of the size of the
document, with "1" being the document itself.
Other features included in this release are:
* Incremental update -- VTD-XML allows one to modify content of XML
without touching irrelevant parts of the document.
* Content extraction -- VTD-XML also allows one to pull an element
out of XML in its serialized format. This can be an important
feature for partial signing/encryption of SOAP payload for
WS-security.
In the upcoming releases, we plan to add the persistence support so
that one can save/load VTD to/from the disk along with the XML documents
to avoid repetitive parsing in read-only situations. XPATH support is
also on the development roadmap. However, we would like to collect as
many suggestions and bug reports before taking the next step.
Your input and suggestions are very important to make VTD-XML a truly
useful XML processor.
Thanks,
Jimmy Zhang
- 4
- grid of JLabelsI want to make a grid of JLabels. I want to have 4 rows and 4
columns.Any ideas?
thanks in advance
- 6
- Spring/Tomcat/Ant/Java developmentHi there,
I am trying to build my first application with the Spring framework,
Apache Tomcat and Ant. I am having trouble accessing the application.
When I try to build it with Ant I get this error:
/home/workspace/springapp/build.xml:78: taskdef class
org.apache.catalina.ant.InstallTask cannot be found
Here is my build.properties file:
appserver.home=home/apache-tomcat-5.5.20
appserver.name=tomcat
deploy.path=${appserver.home}/webapps
tomcat.manager.url=http://localhost:8080/manager
tomcat.manager.username=<username>
tomcat.manager.password=<password>
And build.xml (just where the problem is occuring, since the whole file
is rather lengthy):
<taskdef name="install"
classname="org.apache.catalina.ant.InstallTask">
<classpath>
<path
location="${appserver.home}/server/lib/catalina-ant.jar"/>
</classpath>
</taskdef>
<taskdef name="reload"
classname="org.apache.catalina.ant.ReloadTask">
<classpath>
<path
location="${appserver.home}/server/lib/catalina-ant.jar"/>
</classpath>
</taskdef>
<taskdef name="list" classname="org.apache.catalina.ant.ListTask">
<classpath>
<path
location="${appserver.home}/server/lib/catalina-ant.jar"/>
</classpath>
</taskdef>
<taskdef name="start"
classname="org.apache.catalina.ant.StartTask">
<classpath>
<path
location="${appserver.home}/server/lib/catalina-ant.jar"/>
</classpath>
</taskdef>
<taskdef name="stop" classname="org.apache.catalina.ant.StopTask">
<classpath>
<path
location="${appserver.home}/server/lib/catalina-ant.jar"/>
</classpath>
</taskdef>
Does anyone have a clue as to what I'm doing wrong??
Many thanks,
Courtney
- 13
- destructor neededI have objects that are added as listeners
to various system events (such as change of
language or units etc.).
To subscribe to such events I typically call
someManager.addListener(this); and the "this"
object will be added in a subscription list
of someManager.
My problem is when these objects are no longer
needed. Normally they would be GC'd, but because
of the subscription references they are not,
and the memory is in effect lost.
My current approach is to have a destroy()
method on these objects where I unsubscribe
to system events (removeListener). I am then
forced to think C++ and figure out when the
object actually dies and call the destroy()
method there, which is a pain as it may
include calling destroy() of children objects
etc. and in general it will be very hard to
get rid of them all.
As I assume my architechture is commonplace,
some of you might have a brigther solution
to the problem?
Thanks!
- 13
- Comparing two long numbersJohn B. Matthews <email***@***.com> wrote:
>> I meant (Math.sqrt(5.)-1)/2, which is theoretically the same, but
>> numerically more stable, since the divisor is simpler.
>> But then it would be Math.PHI, and at least as exact as each of the
>> formulae, if not better than both. :-)
> You're right: I inverted but didn't simplify! But isn't
> (Math.sqrt(5.)-1)/2 equal to 1 / phi?
IIRC, PHI is the one with a "1" before the decimal point, so, yes,
your aspect ration was near 1/PHI actually. The other solution
of "x = 1/x + 1" is -1/PHI (-0.618...)
Just hold the height fixed, and make the width of your component
<wish>Math.PHI</wish> times longer. Or if really the width is
given, then make the height a PHI'th.
PS: I think we should think about ending this subthread, shouldn't we?
- 13
- 13
- Multiple Inheritance In Javahi everyone
this is my first post since i joined the group a week ago.
I m working with java for a year now since i come from a C++
background i can't help comparing the two languages.
While studying for java i found many books stating that java does not
support multiple inheritance i don't fully agree with this notion
(please don't hate me for that).
Though it is true that one cannot extend more than one class at a time
which makes perfect sense
since all the classes in java are derived from Object class and
multiple extensions would
cause multiple objects of Object to exist in the code which could be
undesirable.However java could
have provided a concept similar to virtual base classes in C++ but it
would have to be implicit like the extension to
the Object class and moreover multiple calls to the virtual base
class's(Object) constructor would have to be avoided.
(in C++ the compiler donot call the constructor of a virtual base class
from immediate derivations
rather it allows the class which is extending multiple derivations of
the virtual base class to call its
constructor directly, something which is not legal for ordinary base
classes) .Java could not provide a solution like this
since the only way to call the superclass constructor is by keyword
super which can call the constructor of
the immediate superclass only.So it is true that allowing multiple
extensions would have caused more problems
than it could solve.Still while creating patterns multiple inheritance
is sometimes inevitable.The solution to this
problem is interface.An interface in java is used to create a model of
a class,it just declare the behaviour(methods) that
a class must implement.It is worth noting that code reusabilty ,a
criteria generally used to define inheritance,while implementing an
interface is nil.That is why implementing an interface is not qualified
as inheritance.However if you have ever indulged yourself in creating
design patterns you would know that inheritance is more than just code
reusability rather in my opinion code reusability is just a consequence
of implementing inheritance in programming languages. Java allows a
class to implement more than one interface in this way a class can
implement 'behaviours' of multiple classes and thus to an extent
solving the multiple inheritance problem(without providing code
reusability).
So the question is that is it alright to say that java does not
support multiple inheritance?
nirmal.
- 13
- Sun J2SE 1.4.2 max heap sizeHi there !
Can anyone confirm what is the max heap size for the VM in Sun's J2SE
1.4.2 SDK (for windows 64b Itanium 2) ?
In the documentation it is mentioned that for Solaris we have a 64b
address space but I couldn't find anything regarding wintel 64b and I
would like to confirm.
Thanks/Brgds
Joao
- 14
- Tutorial on java beansHi,
I am newbie to Java, though I know the syntax, OOP and have done
some small applications using it. Can someone suggest me a useful
tutorial to learn java beans.
Thanks in Advance
- 16
- Creating Forms in JSPHi ,
I want to create a sample aplication in JSP , which consits of
a basic form , and when the user gives in data in the form , the data
should be stored in the database, and then should be retrived back
when required. Can any one please help out in this as im a total
fresher in JSP .
Please help me out in this..
Thanks in ADVANCE
Sagar meesala
- 16
- Clob trim leaves open cursorsHi,
I have a program which inserts/updates hundreds of clob values in an
Oracle database table. I'm getting a "maximum open cursors" error
when I run this program:
ORA-01000: maximum open cursors exceeded
ORA-06512: at "SYS.DBMS_LOB", line 527
To troubleshoot, I tried checking the v$open_cursor table periodically
during the program run by running this SQL query:
select user_name, sql_text from v$open_cursor
The vast majority of the open cursors had the following sql_text
value:
begin dbms_lob.trim (:1, :2); end;
I ran this program before without problems; the only major thing that
I've changed is to add a clob.trim() call, which I realized was
necessary in case the new clob value was longer than the old clob
value.
Below is the method that's being called repeatedly, where
"retrieveClobQuery" is an SQL query to select the clob value, and
"clobData" is the new clob value to be inserted. The same Connection
(conn) is used throughout. A new Statement is created and closed each
time. (I tried rewriting the code to use the same Statement
throughout, but it didn't seem to make a difference.)
public void singleClobUpdate(String retrieveClobQuery, String
clobData) {
Statement stmt = null;
try {
conn.setAutoCommit(false);
stmt = conn.createStatement();
// Use "for update" parameter to lock the row
ResultSet rs = stmt.executeQuery(retrieveClobQuery + " for
update");
if (rs.next()) {
// Get clob value and cast to oracle.sql.CLOB
CLOB clob = (CLOB)rs.getObject(1);
// Write the data to the clob object
Writer writer = clob.getCharacterOutputStream();
writer.write(clobData);
writer.flush();
writer.close();
// trim clob in case new clob contains less data than
previous one
clob.trim(clobData.length());
}
// Commit changes to release the lock
conn.commit();
conn.setAutoCommit(true);
stmt.close();
}
catch (Exception e) {
e.printStackTrace();
if (stmt != null) {
try {
stmt.close();
}
catch (SQLException e) {}
}
}
}
Any help would be greatly appreciated.
Thanks!
- 16
- Starting the RMI Serverhi,
I have a class which tests to see if an rmi server is bound to the rmi
registry, if not it binds it and if the registry is not running it starts
one with
Process child = Runtime.getRuntime().exec("batch file").
then binds the server to the newly running registry
It does this in a while(true) with a break; when the server is bound to the
registry.
This class does what I want. I have now tried to convert this into a bean,
and have all of the variables and the get/set methods to access them via the
ide propery sheet. However, when I drop this onto a project the code runs
(straightaway in the ide forte & beanbox, without me compiling and running
the project I have dropped it into) - ie the while loop runs immediatly and
does not break; - it goes crazy and starts opening windows. What have I
done wrong - I don't think I have changed the code much since the standalone
calss (apart from the get/set methods, replacing strings with String vars) ?
The code which does all the work is in the default constructor (moved from
main in the original class). Does the ide instantiate the bean when dropped
from the palette onto a project? If so, how can I resolve the issue, if not
then why is the code running without me compiling/running the project?
I have also had trouble with the setSecurityManager(new
RMISecurityManager()) and have been tinkering with the polcy files to see if
that is fixable.
thanks
Mike
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| Author |
Message |
Crux
|
 Posted: 2005-2-10 1:51:00 |
Top |
java-programmer, Cell phone java question
Are there any sources of information on Java programming of Nokia phones?
Esp. w/ code examples about IRda ja network connetions...
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Index ‹ java-programmer |
- Next
- 1
- Elipse and ATG DynamoGreetings,
I am new to Eclipse and am hoping to get it to work with ATG Dynamo.
Has anyone used Eclipse in conjunction with ATG's application server?
Eclipse does not seem to support JHTML syntax highlighting. Am I
wrong? Or is there a plug-in somewhere? Thanks.
-jay
- 2
- abstract vs. finalLew wrote:
> It is not the compiler's responsibility to find test code; it's the compiler's
> responsibility to check the compilability of the artifact itself.
>
> Your idea that there should be a tool, perhaps as part of JUnit or similar
> framework, to check for test coverage is a good one.
(Isn't "test coverage" a stronger notion that just "every entity has a test",
more like "every /code path/ has a test"?)
> You could use the presence of such a tool as an evaluative factor in choosing
> an IDE.
>
> But it is no part of what the compiler should do.
Clearly we have different opinions on what compilers "should", or
perhaps "should not" do. I think it's clearly /useful/ for a compiler
to [be able to] note that there's no use made of some declared entity [1]
in some codebase and I would not apply a "should not" to remove a
useful feature. (Usual tradeoff remarks apply.)
I think I'm done.
[1] I spelled `entity` "thingy" in earlier posts, for want of remembering
the word; I'm not trying to change what I meant.
--
Chris "and you've got to be ready" Dollin
Hewlett-Packard Limited Cain Road, Bracknell, registered no:
registered office: Berks RG12 1HN 690597 England
- 3
- Mouse position while drag&drop-operationHi swing experts!
I have the following problem:
I want to move a custom Transferable via Drag&Drop from a JTree to a
JPanel.
The transferable should be shown on the JPanel on the position the
mouse is released.
The trouble is, I can't determine the mouse position on the JPanel.
The mouseListener and mouseMotionListener-routines on the JPanel
obviously don't work while in a standard-java-drag&drop operation.
For example: The JPanel doesn't fire a mouseEntered(..)-Event, when the
panel is entered during a drag&drop-operation.
So, without Mouse-Events, how do I get the drop-coordinates relative to
the JPanel?
Any clues?
Thanks in advance! Your help is very appreciated.
Best,
Michael
- 4
- RandomAccessFile vs. FileChannelAside from memory mapped files for very large files, is there any
benefit between using the RandomAccessFile class and the FileChannel
class? They seem to be abstractions of the same low level I/O.
- 5
- xp sp2 download problem would someone please explain to me why this routine work
on clients ranging from windows (including XP), to linux, but don't work in
my winXP clients that install SP2 ??? the download window don't appears.
OutputStream out = response.getOutputStream();
response.setContentType("application/octet-stream");
//* response.setHeader("Content-Disposition","attachment;
filename=\"" +request.getRequestURI()+ "\";");
FileInputStream fis = new FileInputStream(nomeFile);
byte[] buffer = new byte[1024];
int byteLetti;
while((byteLetti = fis.read(buffer)) != -1){
out.write(buffer, 0, byteLetti);
}
out.flush();
out.close();
fis.close();
thanks!
maz
- 6
- You'll be alright.Hi Pandora Xero,
Even though it was more than obvious to everyone,
you felt compelled to make this confession:
" If I'm talking about anything,
I'm talking out my ass. "
Stick in there kid, You'll be alright.
P.S.
Can I help you get an ISP ?
Google is the mark of a troll.
- 7
- Connecting J2ME application to Oracle databaseHello,
For my study I have some questions about Java J2ME:
1. Is it possible to develop a J2ME (CLDC/ MIDP) application, which has a
direct connection to a Oracle database?
2. Is there a way for using JDBC within a J2ME (CLDC/ MIDP) application?
Greetings,
Dennis
- 8
- Struts Rapid DevelopmentHi,
I'm looking for a tool, which lets me build web applications using
struts in a rapid development manner.
I know that there exist several tools out there, however I focusing on
the commercial ones, like:
- Camino
- Adalon
- Struts Studio
Can somebody recommend one of them? Which of them is the most
sophisticated and feature reach, when it comes to building large
webapplications?
Thanks,
Fritz
- 9
- Java Interview Questions With "ANSWERS"Hi Friends,
Here is the link for "Java Interview Questions". I hope it will be
useful for all.
I collected the ANSWERS also. So, You can find answers also. Forward
the link to your friends.
Visit the following site :
http://metajai.googlepages.com/
All the Best
Yours Friendly,
Jai
- 10
- 11
- Possible to store JSP output as a string?Greetings all,
Ultimately I'd like to use JSP/JSF for templating, very similiar to the
way I do now with FreeMarker.
I have a chunk of HTML which looks exactly the same on the web and in
email. I'd like to reuse the same template for both.
I've searched around and haven't been able to find a solution to my
problem. I could screen-scrape it, but yuck. Am I stuck with
FreeMarker/Velocity/Etc?
Thanks much!
Jeff Rodriguez
- 12
- Acknowledgment class/deviceWe assume of having a device that generically we model with the Device
class and that will be best specified with the class VCR extension of
Device.
Moreover we assume of having an application (class) Host that knows the
class Device but not VCR;
I would to make so that the device recognizes himeself (based on its
property/features) and that the class Host make an istance of VCR.
Something like
Device dev = new VCR(... pars ...);
In practical on different devices I'll have the same classes Device and
Host and moreover for everyone device I'll have a specific class
extension of Device (is VCR, PC, Freezer etc.).
The class extension could be in one specific folder.
How to make?
Also ideas, suggestions, link
thanks
- 13
- GET and POST in jspHi,
I've been trying to get two parameters passed from a html to a jsp
page. I can read the correct values of the passed parameters but
I am having difficulties distinquishing between those values in an
if-else statement.
The idea is, I need my jsp page to know how the call to it was made. It
can be an INPUT or a VIEW mode.
I've got an entries.html which is:
<html>
<body>
<form action="DocView.jsp" method="POST" accept-charset="UTF-8">
Enter a document of type:
<SELECT NAME="doctype" SIZE=1>
<OPTION VALUE="article">article
<OPTION VALUE="book">book
<OPTION VALUE="manual">manual
</SELECT>
<INPUT TYPE="submit" VALUE="Go">
</FORM>
<BR>
<form action="DocView.jsp" method="POST" accept-charset="UTF-8">
Or view an existing document with id
<SELECT NAME="docid" SIZE=1>
<OPTION VALUE="1">1
<OPTION VALUE="2">2
<OPTION VALUE="3">3
</SELECT>
<INPUT TYPE="submit" VALUE="Go">
</FORM>
</body>
</html>
and a DocView.jsp one:
<%
String doctype = request.getParameter("doctype");
String docid = request.getParameter("docid");
String mode = "";
if(docid != "") {
mode = "VIEW";
}
else if( doctype != ""){
mode = "INPUT";
out.println("doctype = " + doctype + ", mode = " + mode +"<BR>");
out.println("docid = " + docid + ", mode = " + mode);
%>
The if-else statement should identify the type of call was made to
DocView, based on that, actions will be taken.
The code is just to demonstrate the idea of what I am doing. The
actuall code reads data from a MySQL database.
As a result of Docview.jsp I get the correct value of docid if I chose
an id value or a null if not. The same with doctype,
either the choosen doctype is displayed or a null. But the variable
mode does not change.
It is alway VIEW. Or actually it always gets the value that assigned
first to it. If I change else-if with the if statement, then the mode
will always be INPUT.
Now that leads to the conclusion that mode has to be reinitialized! but
How?
I can do the same thing with PHP, but there I can use $_GET['param']
and $_POST['param'] and different if-else statement, and it works
perfectly. Here is just a snip if the statements in PHP (sorry for
having to post a php code, but this might clearify my problem more).
$mode="";
$docid=$_GET['docid'];
$doctype=$_POST['doctype'];
if($docid!="") {
$mode="VIEW";
} else {
$docid=$_POST['docid'];
if ($doctype!="") {
$mode="INPUT";
} elseif ($docid!="") {
$mode="EDIT";
}
}
(the EDIT mode will be added to the jsp later), but this code does
exactly what I want. how can realize the same in my jsp code?
I appreciate any help on that.
Thankfully,
Michael
- 14
- A splash screenI am trying to create a splash screen. I would like it to be visible for a
few seconds while the application is initialising. After a timer expires,
the splash screen will close automatically. I have all of this working just
fine.
However, at some point during the application initialisation, it creates the
main window. When this occurs, the main window appears on top of the splash
screen. I would prefer that the splash screen be "top most" when this
occurs.
I have tried various combinations of toFront() and toBack() with no success
whatsoever.
How can I keep my splash screen topmost - preferably without having to mess
with "lost focus" type of events? In VC++, I could do this by creating the
splash screen window with the "TOPMOST" attribute set - but I can't find a
similar attribute in the java window classes.
TIA - Glenn Mc
P.S. For what it is worth, I have attached some snippets of the code I am
using. SplashPanel extends JPanel and contains all of the components making
up the splash screen.
public class SqlManEditor extends JFrame {
private static JWindow splash;
private static void showSplash (final int duration) {
/* final JWindow */ splash = new JWindow ();
SplashPanel content = new SplashPanel ();
splash.setContentPane(content);
splash.pack ();
// Center the splash screen in the display.
Dimension screen = Toolkit.getDefaultToolkit().getScreenSize ();
int x = (screen.width - content.getWidth()) / 2;
int y = (screen.height - content.getHeight()) / 2;
splash.setBounds (x, y, content.getWidth(), content.getHeight());
Thread r = new Thread () {
public void run () {
// TODO: Figure out how to get the splash screen
to be "topmost"
// Currently when the main window is
created, it will appear
// in front of the splash screen.
splash.setVisible (true);
// wait for the specified number of milliseconds
try { Thread.sleep (duration); } catch (Exception e) {}
// When the timer expires hide the window and get
rid of it
splash.setVisible (false);
splash = null;
}
};
r.start ();
}
public static void main (String [] args) {
showSplash (5000);
SqlManEditor s = new SqlManEditor ();
s.toBack (); // After these two lines of
code execute
splash.toFront (); // s is in front and splash
is still in back!
}
}
- 15
- javax.comm - SerialPort ProlemHi,
I tried to install the comm-extensions (with Java 1.5) and copied my files:
win32com.dll -> \myjdk\jre\bin
javax.comm.properties -> \myjdk\jre\lib
comm.jar -> \myjdk\jre\lib\ext
I'm using Eclipse.
Now to my problem:
A piece of my code:
portList = CommPortIdentifier.getPortIdentifiers();
try {
portId = CommPortIdentifier.getPortIdentifier( name );
} catch(Exception e) {System.out.println("error on comportIdentifier");}
After executing the first line portList is empty and 2 lines later a
NoSuchPortException is thrown -
it seems that I did something wrong because I don't get any portIdentifiers
at all ... but after searching for hours in the internet I only found hints
where to copy the files but nothing more ...
I would be glad if someone could help me!!
btw: I'm using WinXP
Thomas Pototschnig
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