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Easy Learn Java: Programming Articles, Examples and Tips - Page 159


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Java Newsletters: Java Newsletters Archive: 171

Go to all tips in Java Newsletters

=== [ The Java FAQ Daily Tips, weekly publication ] ===

Issue No: 171 8 July 2003
13563 subscribers

Foreword: Excuse me for possible mistakes. English is not native language for me.

In this issue:
  • 1. When I use InetAddress.getByName if a lookup to the name service failed then ...
  • 2. In Ukraine first day of week is Monday but not Sunday
  • 3. Performance testing has shown that the finalize methods in the channel classes...
  • 4. Latest posts on our message board
  • 5. Link to Java FAQ

  • Hello dear friends!

    Tip 1

    Question: When I use InetAddress.getByName if a lookup to the name service failed then all subsequent lookups of that hostname fail as well for the lifetime of the virtual machine...
    It looks like negative lookups are cashed. What is solution? Is it more bugs I should be aware of?

    Answer: Use latest J2SE 1.4! Prior to J2SE 1.4 negative lookups were always cached. This has changed in 1.4 so that by default if a lookup fails it's possible for a subsequent lookup to succeed. This is particularly important in dial-up environments or environments where the name service is not reliable.

    Also prior to J2SE 1.4.1 the java.net.InetAddress.getLocalHost() would cache the lookup of the IP address of the local machine for the entire session of the application. This behavior poses a problem for applications running on machines that are connected to the internet via a dial-up connection or machines that acquired their addresses through DHCP. This has been corrected in 1.4.1 so that the local IP address is no longer cached. InetAddress.getLocalHost() will return the correct IP address for dial-up connections as well as for DHCP

    Prior to J2SE 1.4 the InetAddress.toString() would perform a lookup via the name service if the hostname wasn't previously resolved. This is no longer the case in 1.4 and toString will return immediately. If the hostname is not resolved the returned string will contain the dotted IP address only.
    Applications that depend on toString() returning a string with the resolved hostname should be aware of this correction in 1.4

    Java wimps please close your ears ... For the Java programmer who
    thought he knew everything there was to know about Java, have a
    look at the most advanced Java newsletter archived on the website
    http://www.smotricz.com/kabutz Guess what, it won't even cost you
    anything! Subscribe today - you won't be disappointed.


    Tip 2

    Question: In Ukraine first day of week is Monday but not Sunday

    By defaults in the calendar object obtained with locale ua_UA getFirstDayOfWeek
    () function return SUNDAY as a first week day... Java version is 1.3.1_01

    Answer: Yes indeed, according to this list:
    http://www.pjh2.de/datetime/weeknumber/wnd.php
    the first day in Ukraine is Monday. For those who does not know will say that in many countries Sunday or even Saturday is first day, for example in Egypt - Saturday and in Argentina and Brasil - Sunday...
    It was a bug since according to ISO 8601 in all European countries a week starts with Monday...
    I know that with Hungarian calendar was the same bug... In latest 1.4.1 and beyond the bug is fixed.


    Tip 3

    Good to know: Performance testing has shown that the finalize methods in the channel classes impose a significant GC penalty upon server-type programs that must deal with
    thousands of new open channels per second.

    And now in J2SE 1.4.2the finalize methods of the primitive channel classes (SocketChannel, ServerSocketChannel, etc.) have been removed . Additional performance test measurements revealed that the presence of these methods imposed a significant (factor of 100) garbage-collection penalty upon server-type applications that process thousands of new open channels per second. User code that deals in channels should be carefully written to close channels explicitly rather than rely upon the garbage collector to do so.


    Latest posts on our message board
    Trying to connect to mysql!?

    I´m trying to connect to a mysql database from a applet, but I get this error:

    Unable to connect to any hosts due to an exception:java.security.AccessControlException:access denied.....and so on.

    What´s that? It used to work in postgres.
    What should I do?

    /Grandma
    please help here

    Java Layers

    Hi,
    I have a java menu, and also java visual effects on our logo. at http://www.blueislanddivers.com/testlogo.htm but cannot make the menu bar remain on top view over the logo. I'm more of a 'mechanic' than programmer, certainly not an expert. Any help would be greatly appreciated.

    Sean Mckenna

    please help here

    Connect 4 or 4 in a Row HELP

    Hello,


    I'm creating a school project, the game connect 4, or four in a row. I have everything done, except for where the program checks wether the

    lines are 4 in a row or not. Can anyone help? Here's the code:
    continues here

    Applet Menu

    I can't run one applet with a menu, where itemmenu don't call the function related.

    The same menu in the application fashion work, please help me and sorry for mi english

    gustavo
    please help here

    Parallel sorting

    I would like to send me (or give links) of java code
    relative to :
    sorting an array of integers in parallel
    please help here

    Almost no hair left! NullPointerException in EventDispatchThread.

    I get this error after app has been running a while.
    What is the problem and where can I fix? It doesn't happen on my dev machine, but only on the production system.
    Help will be much appreciated!
    Quigrim

    java.lang.NullPointerException
    continues here



    9 comments | Printer Friendly Page  Send to a Friend | Java Newsletters | Score: 0
    Posted by jalex on Monday, February 02, 2004 (16:01:11) (2706 reads)

    Java Newsletters: Java Newsletters Archive: 169

    Go to all tips in Java Newsletters

    === [ The Java FAQ Daily Tips, weekly publication ] ===

    Issue No: 169 3 July 2003
    13435 subscribers

    "...if you have no mentors around in the initial stages."
    "This book has saved me hours of research...""


    Foreword: Excuse me for possible mistakes. English is not native language for me.

    In this issue:
  • 1. Where can I find sample code for J2EE guidelines, patterns, and code for end-to-end Java applications?
  • 2. What is date of Java birthday?
  • 3. Latest posts on our message board
  • 4. Link to Java FAQ

  • Hello dear friends!

    Tip 1

    Question: Where can I find sample code for J2EE guidelines, patterns, and code for end-to-end Java applications?

    Answer: J2EE Patterns catalog is set of practical solutions to recurring problems! J2EE Patterns not only help you build simpler systems that work, but they also help you build beautiful programs
    J2EE Patterns catalog is here:
    http://java.sun.com/blueprints/corej2eepatterns/Patterns/index.html


    Tip 2

    Question: What is date of Java birthday?

    Answer: May 23, 1995. John Gage, director of the Science Office for Sun Microsystems, and Marc Andreessen, cofounder and executive vice president at Netscape, stepped onto a stage and announced to the SunWorld audience that Java technology was real, it was official, and it was going to be incorporated into Netscape Navigator, the world's portal to the Internet.

    At that time, the entire Java technology team, not yet a division, numbered less than 30 people.

    More about early history of Java please read here:
    http://java.sun.com/features/1998/05/birthday.html

    --
    John


    Latest posts on our message board

    bloking Java plugin in applet tog

    How can the default call of the java plugin on the applet tag be blocked so an applet can be run without the plugin. I have an applet that runs fine with out the plugin but stalls with it.
    help here


    Almost no hair left! NullPointerException in EventDispatchThread.

    I get this error after app has been running a while.
    What is the problem and where can I fix? It doesn't happen on my dev machine, but only on the production system.
    Help will be much appreciated!
    Quigrim

    java.lang.NullPointerException
    at javax.swing.plaf.basic.BasicProgressBarUI.getGenericBox(BasicProgressBarUI.java:477)
    continues here


    Java Web Start

    I have a problem with An Application that is launched by
    web-start.

    I would like to load class-files from jar's or zip-files that are
    not part of the spec. in the Applications jnlp-file.

    I can download the jar from a web-server and place the jar's/zip's in a catalog. And then try to instance the classes that i want from the jars/zips.
    I have tried to write my own class-loader. And it works ok if
    i run the application locally ( not from web-start ).
    continues here


    Watch Training Video on Enterprise JavaBeans For Free(DSL version)

    Hi all,
    We just posted new Training Video on Enterprise JavaBeans(DSL version),it may be helpful for you all.
    Thanks

    Direct Url:
    continues here


    Help in JTextPane

    Hi,

    I am displaying a html file in JTextPane, When I do changes in that file, click on send, These changes should be sent to other user which highlighted text which is changed, I know the highlighting part, but how to send only the changes which have been made, I don't know. I have implemented DocumentListener but I don't know why it is not responding when I attach a HTMLEditor kit with JTextPane
    help here


    JPanel on top of another JPanel

    I've got two JPanels. And I want to show one on top of the other:

    http://www.wflyers.nl/java.gif

    The red one has to be on top of the big bleu JPanel.
    I've tried JLayeredPane() already, but that failed.
    Does anyone has got an idea how to fix this problem.
    help here


    Updating randomAccessFile

    Hi again, ne wday new problem.
    I have a GUI that takes the attributes for a student, name, address etc and stores it to a random file. I everything works fine, but now I have to be able to update the information in the file. When I veiw the student information in the studentpanel, I should be able to edit the textfields and click on an update button that will update the file. I don`t want to append on to the existing file, I just want to overwrite it with the new information...at least thats what I think it should be doing.
    I created my update button and Now I am in the process of figuring out the actionevent for it,,,,except I do not have a clue, I havn`t even been able to find any basic examples of this.
    This is what I have so far.
     

    code:

    if (e.getSource() == jbtUpdate)
    continues here


    comments? | Printer Friendly Page  Send to a Friend | Java Newsletters | Score: 0
    Posted by jalex on Monday, February 02, 2004 (15:59:42) (2605 reads)

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