Question about Java Micro Edition

Hello,
I am interested about writing a program for PDAs. These seem to be running the Java Micro Edition, so I guess this is a good choice. But what about programming the GUI with the j2me? Afaik, it does not support swing, and the specifications are so full of abbreviations that I do not undertand that I really don't know other than to simply ask here about the possibilities of GUI programming with j2me, is there a "standard" gui library for j2me, or is it device-dependant, and is it possible to install the j2me under windows/linux for developing and testing purposes?
Help please.. ;-)
Thanks
Jan

thx :) J2ME seems to be very interesting. But zeb is right with the post in the discussion thread for this article, "where to start" is an important questions. So please, sun, make it easier for us to us (hobby-)programmers to adopt J2ME..
I found this one alternatively:
www.ewesoft.com
does anyone have experiences with it?
Jan

Similar Messages

Help in Java Micro Edition SDK 3.0 EA...

Hi, I am using the Java Micro Edition SDK 3.0 EA version. I have a problem that when i write code to access the RecordStore, it does not seem to work. Plus, for the FileConnection programs, where do i store the accessible file structure on the disk. In WTK, it was under the appdb of the specified emulator, but i dont know the path from where the filesystem is mounted.
Another problem is that, I want to create a simple Java class in a separate file in the SDK. But, when i right click and select "New" on the project, it only shows options to create MIDlets or MIDlet Canvas files..
Any help will be highly appreciated. Thanks..:-)

About the file structure in FileConnection, in NetBeans it is in C:\Documents and Settings\[your user name]\j2mewtk\2.5.2\appdb\root
You can change the root folder if you go to "manage emulators", then in "tools & extensions", click on "open preferences" and then select "storage". I don't know if SDK 3.0 has it too... sorry... I switched to NetBeans because it has more options...
About creating a separate file, I always did it manually, adding a .java file to the src directory (with notepad, for example). Again with the full NetBeans, right-clicking in the project gives you an option to create a new Java class so you don't have to do it manually.
About the record store, I don't know, sorry... But I answered 2 of 3! :)

Question about Java's HttpServer: Threading? Backlog?

Hello,
I have two questions about Java's HttpServer (com.sun.net.httpserver). From the JavaDoc:
>
Management of threads can be done external to this object by providing a Executor object. If none is provided a default implementation is used.
>
How can I get information about the default implementation in 1.6.0_13? Do you know the behavior? From my observations, the default implementation uses no Threads, meaning every request is handled in the same Thread, this results in handling the requests to the HttpServer one after another.
Is this right?
The second question is about this, also from the JavaDoc:
>
When binding to an address and port number, the application can also specify an integer backlog parameter. This represents the maximum number of incoming TCP connections which the system will queue internally. [...]
>
When setting the backlog to -1, it uses the systems default backlog. How can I determine the systems default backlog? Can some lines of Java code reveal it (there is no getBeacklog() method)? Or is it up to the Operating System (we use Redhat Linux)?
Thanks a lot for your help!
Regards,
Timo

How can I determine the systems default backlog?You can't. There is no API for that even at the C level.
Can some lines of Java code reveal itNo.
Or is it up to the Operating System (we use Redhat Linux)?Yes. Linux provides a large default. It seems to be at least 50 on most platforms. This is not something you should be worrying about.

Java Micro Edition and maps

Hello all,
I have recently mashed together a desktop application using swinglabs JxMapViewer. JxMapViewer basically does all the map downloading, rendering, etc for me and lets me concentrate on my application.
Now I wish to port my application to Java Micro Edition, but JxMapViewer unfortunately doesn't work in Java ME. So I need a replacement.
Does anyone know of a vendor independent (as in can load maps from many different servers, google, yahoo, nasa) mapping api that is designed to work under Java ME?
Jaxie

Might better go here http://wireless.java.sun.com/
or here http://forums.java.sun.com/wireless/

Three questions about Java and Ftp

Hello, i've the following questions about Java and Ftp:
1- .netrc file is in $HOME directory but i can't access to this directory from java code. The following line producesan Exception (directory doesn't exists)
FileWriter file = new FileWriter ("$HOME/.netrc");
2- .netrc file must have the following permissions: -rw- --- --- but when i create the .netrc file the following permissions are on default: -rw- r-- r--, how can i change this permissions? (In java code, i can't use chmod.....)
3- Are there any way to pass parameters to a .netrc file? If i get to do this i needn't change the permissions because i can't modify or create/destroy this file.
Thanks in advanced!!!
Kike

1- .netrc file is in $HOME directory but i can't
access to this directory from java code. The
following line producesan Exception (directory
doesn't exists)
FileWriter file = new FileWriter ("$HOME/.netrc");$HOME would have to be replaced by a shell, I don't
think you can use it as part of a legal path.
Instead, use System.getProperty("user.home");
Ok, thanks
2- .netrc file must have the followingpermissions:
-rw- --- --- but when i create the .netrc file the
following permissions are on default: -rw- r--r--,
how can i change this permissions? (In java code,i
can't use chmod.....)Yes, you can: Runtime.exec("chmod ...");
I need to use estrictly the .netrc with -rw- --- --- permissions
Yes, i can use Runtime.exec ("chmod ..."); but i don't like very much this solution because is a slow solution, am i right?
3- Are there any way to pass parameters to a.netrc
file? If i get to do this i needn't change the
permissions because i can't modify orcreate/destroy
this file.I don't think so. Why do you need the .netrc file in
Java at all? Writing a GUI frontend?I want to use automatic ftp in a java program and FTP server, the files and path are not always the same, so i can:
- modify .netrc (for me is the complex option)
- destroy and create a new .netrc (is easier but i have permissions problem)
- use .netrc with parameters but i haven't found any help about it
Thanks for your prompt reply!!!!
Kike

Java Micro Edition and Smart Phone Programming

I have successfully installed Java 2 Micro Edition 8.1 on my computer, and the Micro EditionNnetbeans plugin in.
I am programming with netbeans. In order to create a new project, I need to have the
Java ME Embedded Emulator (Oracle) going on a near-enough virtual mobile phone. I can either
virtualise my phone entirely, or used a real phone plugged in.
-Is there a command line tool that comes with my version of micro edition java
which can generate a JAD file from a completed, manifest-written executable
.Jar file?
-Can someone tell me what to do with the emulator to get it running in either mode,
given that I know all the manufacturing details about my particular Smart Phone?

It depends on how advanced the midlet will be. If standard components are used, the app should work everywhere, otherwise it need to be tested (it need to be tested always). If You need to write a midlet with Location API You first need to find a device that has this api implemented to test your application and the start writing. One importatnt thing, if a device in it's specification has written that it support Location API it doesn't have to mean that it's supported fully, some functions may not be implemented. As You can see here for instance. If You are not familiar with midlets start with a tutorial for beginners and after finishing try using more advanced APIs.

Questions about Java Servlets and JSP

Hi,
I'm a confident Java Programmer (and really enjoy using this language) but am very new to Java servlets and Java Server Pages.
I have previously worked with Perl on my web projects (simple 'league' style voting pages). I read in my 'Core Java' book that I should no longer use perl or even cgi.
I need to know more about Java servlets and Java Server Pages so I can make the switch to a 'real' programming language.
I have a few questions:
How should I start to learn JS and JSP?
How applicable will the java knowlegdge I have already be?
Are JSP common on the world wide web?
What tools do I need to start? (I currently develop in JBuilder and have Java 1.4.1 Standard Edition)
Is it likey my web host (and others) will support JSP?
Thank-you very much for helping a novice get started,
Regards,
Paul

Hi, Steve ...has to be frustrating! But do not despair.
Let's suppose the servlet it's named MyServlet on package org.servlets
WEB-INF should look:
WEB-INF
classes
org
servlets
MyServlet.class
web.xml
web.xml file should have this two declarations:
<web-app>
<servlet>
    <servlet-name>MyServlet</servlet-name>
    <servlet-class>org.servlets.MyServlet</servlet-class>
</servlet>

<servlet-mapping>
    <servlet-name>MyServlet</servlet-name>
    <url-pattern>/MyServlet</url-pattern>
</servlet-mapping>

</web-app>Now, once the container starts (Tomcat?), you should be able to see that servlet in:
http://localhost:8080/[my-context/]MyServletAnd what my-context is? The web application context. This string should be empty if your're deploying to the root context, otherwise should the context name. In Tomcat, deploying to root context defaults to using webapps/ROOT.
Sorry for my English, but I felt the need to answer your request. I hope it helps despite my writing.

Question about Java apps structure

Hello guys,
I'm a professional C++ programmer and I would like to start learning Java. I'm reading about Java from here and there and would like to ask you about how a java program is structured compared to C++.
So in C++, I have main.cpp (or any other file name, doesn't matter), which contains a the main() function, and I have .h and .cpp class files that I instantiate (basically) in my main function to get my program to work.
In Java, I'm confused and can't really find the "general" rule to how stuff are organised. I noticed that every class has a main function (why?), and there's no global scope. And "somehow", file names must exactly be equal to the class names.
The question is: how are Java files of classes (and other stuff, if available) are arranged to create a program? What's the standard why? And How can I have many classes together in a single main()?
Thank you for any efforts :-)
Edited by: 927494 on 13.04.2012 07:02
Edited by: 927494 on 13.04.2012 09:10

Thank you guys for the replies. I still have some more doubts :-)
Do I have to have a file for the implementation and a file for the definitons, like cpp and header files? or just everything inside the class?
Why does Netbeans fail to compile when I change the class name? what should I change with the class name in general to have it compile correctly? From what I understand till now, the top level class's name (the class with the main() function that's gonna be executed) has to be equal to the file name (and I got that this is the sufficient condition for the app to compile), while the same file can have more classes if I wish. Did I get that right?
I don't know if I get that right too, we pass only a SINGLE class/file to the compiler, and it automatically resolves ALLLL the included files automatically, unlike C++, where all cpp files have to be passed to the compiler/makefile to create object files, and then the executable is created after linking all those object files with the libraries together. i.e.: Java doesn't really need a makefile because making is really simple with only 1 filename. True?

Some questions about Java deployment steps and techniques

All my java experience is coding and testing in my local machine (where, of course, a jre is available), but ... when I deploy to other people, they may not have a jre or they may have a different version of it than the one needed to run my application. I've read different stuff online including jars and java web start but still I have many questions.
(1) first one first, Sun contradicts common sense, when it says that i can redistribute my own customized light version of their jre by taking out some files (java.sun.com/j2se/1.5.0/jre/README). there are two ways for me to get a jre: Way one is by downloading one from Sun, the download comes as an *.exe file and I don't see how I can take files out of it, so do you know how?. Way two would be by simply copying the set of files i choose (according to that Readme) from my current jre installation (the one on my \java\jdk\jre directory), does this make sense?, (if you're under windows) doesn't an installed version of a jre need a couple of dlls plus some new registry entries?, this contradicts common sense, if I'm not wrong, that Readme is a nonsense, but since that readme is at each of us jre installation \java\jdk1.x\jre\Readme, it can't be a nonsense, therefore I'm wrong, therefore the answer is either Way 1 or Way 2, HOW? ... or maybe there's a Way 3?
(2) Say I never read that Readme so I download the jre (as an exe) to bundle it along with my application in a jar ... now I'll give my neighbor either a jar with two exes or two exes jars ... is there a way to make a jar so that two files get executed? ... if the answer is No and I have competition from a second neighbor, then I believe I'm asking my first neighbor to choose my application based on our friendship, that's not reasonable if we are doing business, so Java loses.
(3) Say that my application is a single executable file like this,
class X{
public static void main(String[]$$$){
System.out.println("Console, where are you?");
At this point, say that my neighbor accepted the two executables, he executed the jre.exe and has jre6 in his system, now he double clicks on my X.jar ... it's a console application and jar files are not associated with the java.exe launcher since java 5, but with javaw which doesn't open any console ... how do i make it so a console opens and prints "Console, where are you?" ... do I ask my neighbor-customer to add a couple of lines to his path and open his console and (please) enter java -jar jarfile.jar? ... isn't it too much? ... i hope i'm wrong cause this is kind of discouraging
(4) I've read that by installing a more recent version of a jre on a system that has an older jre (there to help other applications work), I might be causing a problem for the other applications to run ... I guess that's the reason why that Readme kind of encourage to redistribute a "private" version of a jre (one that doesn't come with a java.exe launcher ... any feedback on this?
(5) I'm reading a lot of hype about Java Web Start ... it looks better than the traditional jar/jre deployment ... but setting up a MIME type to *.jnlp, it doesn't come with some free hosting I've checked ... somebody can recommend a free hosting service that allows to set a *.jnlp MIME? (I'll appreciate a suggestion here, cause I would like to test Web Start)... and, anyhow, how you people compare it with the paradigm of the single executable file?.
Thanks. Your feedback is highly appreciated.

jorgelbanda wrote:
..(5) I'm reading a lot of hype about Java Web Start ... It's gratifying to think that someone who wants to deploy apps., has the common sense to search first! You would not guess how I often I hear "I wanna' make an EXE" shortly followed by "What's webstart?".
...it looks better than the traditional jar/jre deployment ... but setting up a MIME type to .jnlp, it doesn't come with some free hosting I've checked ... OK. You cannot define new mime types, but perhaps the site already has it defined. An easy way to check is to upload 'any old file' that ends in .jnlp and use the [mime type checker|http://pscode.org/mime/] to see what content type it is served as.
..somebody can recommend a free hosting service that allows to set a .jnlp MIME? (I'll appreciate a suggestion here, cause I would like to test Web Start)... I'm pretty sure the Google based sites offer it.
Note that I edited the asterisks out of your post, to avoid the forum software parsing half the reply as bold.

Java Micro Edition

I am developing an application for the Palm OS, I am using Suns Studio ONE micro edition. I am having a problem setting the size of an image, I add the Image to ImageItem, ImageItem is a subclass of Item which has a setPreferredSize method, but it tells me it does not recognise the method, According to the API this feature has be included since MIDP 1.0. I also tryed setting the size on a Item object but got the same error.
If there is anyone who can help I would be much appreciated. Or if i am asking this question on the wrong form let us know
Thanks
Noel

Might better go here http://wireless.java.sun.com/
or here http://forums.java.sun.com/wireless/

Question about Java Errors

I have some questions about some java errors
1. what kind of errors are contained in Error class?
2.does this class contain only runtime errors?
3. if the question number 2 is positive, what about InstantiationError which is a compile error and is a subclass of Error.
4.When our program is out of memory, which processes are done for an error to be produced. is the error actually from OS or VM?

I have some questions about some java errors
1. what kind of errors are contained in Error class?An Error is a subclass of Throwable that indicates serious problems that a reasonable application should not try to catch.
2.does this class contain only runtime errors?No
3. if the question number 2 is positive, what about
InstantiationError which is a compile error and is a
subclass of Error.
4.When our program is out of memory, which processes
are done for an error to be produced. is the error
actually from OS or VM?Various - both, depending on where the error occurred.

Question about java-based server app frameworks

Hello, I am working on a Java applet application and would like to choose a Java-based scalable server framework to use within my applcation. I have found a few like xsocket or QuickServer and have a question about other. And, also, which is the one You may advise? Yours sincerely, Slawek

For online gaming server. I first heard of xsocket and started using this, but have the problem with NAT. I now know that I need to initiate connections from client behind NAT (server has a public IP) and send messages from server to client within the same connection. I am doing this the following way (as shown in examples- below), but it appears that server receives messages, but client doesnt. I dont listen on any ports in client application and just need to take advantage of the connection initiated (information go from client to server properly).
Server-
try{ nbc = pool.getNonBlockingConnection(inetAddress, 8090);
try{ nbc.write("|01|______|02|______|03|______|04|______|05|______|06|______|07|______|08|______|09|______|10|______"); }catch(Exception ee){}
}catch(java.io.IOException f){}
Client-
public boolean onData(INonBlockingConnection nbc) throws IOException,ClosedChannelException,BufferUnderflowException,MaxReadSizeExceededException{
String x = nbc.readStringByLength(100);
System.out.println("S >> C = "+x);

From USB to IEEE-1394: question about HD capture, editing, sharing.

I’m new to editing video but have a question about capturing video into Premiere Elements 7. I have been using a Canon HF11 which shoots only in HD and only has USB output to copy video to my desktop. I don’t have a Blu-ray burner yet but I have burned a few projects to DVD, shared video on YouTube, and saved files in .avi and .mpeg to view on computer screens. But obviously I’m missing out on sharing HD on disk at this time. I just bought a Canon XH A1s which shoots both HD and SD on miniDV tapes. And uses IEEE-1394 cable for capturing (to Pre7). I did a 3 minute test project in SD and burned it on a DVD disk. I was very pleased at the results and the ease of editing. I don’t have any HD tapes yet, but when I do what differences will I experience from shooting in HD and then capturing, editing, then to sharing? My current HD processes with the HF11 is slow, occasional low-resources warnings, and less then pleasing results on DVD disks. Thanks for any and all comments and/or suggestions.

Your HF11 is AVCHD format and the Canon XH A1 is HDV MPEG2. AVCHD takes a lot more computer horespower to edit compared to HDV MPEG2... main reason being that AVCHD is more highly compressed giving small file sizes. This is also why you get the low resource and memory alarms while editing.
To shoot HD you do not need HD miniDV tapes you can use the standard miniDV tapes. However the HD tapes are supposed to give fewer drop-outs than the standard tapes but are considerable more expensive. With DV-AVI a drop out would be hardly noticed, but as HDV MPEG2 is a compressed format and the picture relies on information in a number of frames any drop-outs can give a second or so of bad video. That said I have had very few issues with drop-outs. If you are doing a wedding or something important that you do not want to risk then probably better to use a HD miniDV tape.
In the past the advise has been to capture in high definition to get the best quality and then downconvert in the camcorder and capture in DV-AVI... the reason being that older versions of Premiere Elements did not do a good job of the down conversion. Reports on PE7 indicate it is better and that you could use a HDV workflow and burn to DVD as a last stage. This also allows you to export a high definition version of your video to view on a monitor where you can appreciate the higher resolution. Or in the future when you have a Blu-ray burner and player you can burn the file to disc... save doing all the editing all over.

Question about Java SDK 1.5.0 and mobile devices...

Hello, everyone. This is my first time posting on these forums since I usually find the answers I need from old threads (this place is VERY informative and HELPFUL). I wanted to know if it's possible at all to create a program from the Java Standard Edition Development Kit and have it operate on a mobile device or a suitable mobile device emulator? Or is that ony feasible with the J2ME kit? Any revelant response would be much appreciated. Thanks!

A J2SE application will not work on most mobile
devices.I know J2SE applications that don't even work on non-mobile devices.

Question about Java implementation in Linux platform

Hello,
I shall implement one Java program in Linux platform. I'm a newer to linux. Need I install some special software in Linux platform to compile and run JAVA program?
Thank you in advance
java_linux

Sorry, this forum is about Sun Studio, which is a collection of native compilers and tools. About Java, please use Java forum; for example, one of these: http://forums.sun.com/category.jspa?categoryID=5

Question about Java Micro Edition

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