Java

Re: which keyword used for differentiating local and global variable in java.

4-Jan-11 21:31

All variables are defined by their scope, that is to say the block that contains them. Since no variable can exist outside a class there are no globals in Java. Take a look at the Java Tutorials[^] for more information.

Just say 'NO' to evaluated arguments for diadic functions! Ash

TorstenH.4-Jan-11 22:07

TorstenH.

4-Jan-11 22:07

I agree to what the others wrote.

There are some keywords in java you may not use as variable name:
Java Language Keywords @ Oracle.com[^]

But usually those words are highlighted in a special way as you use an IDE like Eclipse or Netbeans.

regards
Torsten

I never finish anyth...

Re: which keyword used for differentiating local and global variable in java.

Ramaiah Raj30-Jan-11 20:16

Ramaiah Raj

30-Jan-11 20:16

Static can be used as a key word to differentiate instance variable and Class variable. But according to the place where its declared can determine whether its local variables or instance variables. But there is no global variables in java.

public class DemoVariable {

private static int a=0; //Class Variable
private int b=0; // Instance Variable

public void print() {
int c =0; // local variable
}

}

Loading a sound file from a jar archive [SOLVED]

Pamodh2-Jan-11 2:59

Pamodh

2-Jan-11 2:59

I'm developing a small game using the Swing Application Framework and I have stored a sound file (to be played when the user clicks something) in the application.resources folder:

resourceMap.getClassLoader().getResource(resourceMap.getResourcesDir()+"Beep.au").getPath();

(Then I use the path text returned to create a new File object which I pass into the AudioInputStream's constructor).
I'm using NetBeans and it works fine when I run it in NetBeans. But when I run it outside NetBeans (by executing the jar file that NetBeans creates) I can't play the sound because a null pointer exception gets generated in the AudioInputStream's constructor.

Can anyone help me out here to figure out what's going wrong?

modified on Monday, January 3, 2011 8:47 AM

jschell2-Jan-11 9:03

jschell

2-Jan-11 9:03

Pamodh wrote:
Then I use the path text returned to create a new File

A File is basically a metadata representation of a file on the file system.

As described it cannot contain data because it isn't in fact a file (because it is in the jar.)

Thus what you are actually doing in your code is creating a reference to the actual file.
And that is why it doesn't work outside of netbeans.

You need to extract the file from the jar as a byte stream and enclose it in a Stream.

Pamodh3-Jan-11 2:46

Pamodh

3-Jan-11 2:46

Thanks for the answer. I tried it but it still didn't work. But then I saw that I had made a small mistake in capitalization of the actual file name. After fixing that and adding in your method, it worked great! Thank you very much!! Smile | :)

jschell3-Jan-11 9:56

jschell

3-Jan-11 9:56

Pamodh wrote:
But then I saw that I had made a small mistake in capitalization of the actual file name

Per your explanation of your code that doesn't fix the problem that I was describing.

To guarantee correctnesss you should test your jar by doing the following.
1. Build the jar
2. Rename the sound file
3. Verify the sound file doesn't exist anywhere.
4. Run your jar

Pamodh4-Jan-11 4:23

Pamodh

4-Jan-11 4:23

I did and it works OK. Thanks! Smile | :)

validation

pancakeleh30-Dec-10 16:46

30-Dec-10 16:46

Needing help in validating textboxes to check if the textbox is null. I am netbeans and doing web application.
Anyone knows where to find tutorial on this?

Richard MacCutchan30-Dec-10 23:00

30-Dec-10 23:00

Well, there is always the obvious place[^].

Just say 'NO' to evaluated arguments for diadic functions! Ash

pancakeleh3-Jan-11 15:56

3-Jan-11 15:56

i am now able to validation textboxes when the textboxes is null a error message will appear.

Right now if the user enter the number 20 and he or she wants to add the number 20 again, an error will occour.

how do i achieve tt?

i tried google however have no clue on how to strt.

Needing help..

TorstenH.3-Jan-11 21:13

TorstenH.

3-Jan-11 21:13

Assuming you've split your code into MVC (Model, View and Controller) - and of course you did so Wink | ;-)

You will store the data somewhere in a object. For this you're using a set-methode.
This is a typical moment for checking integrity of the value:

public void setIValue(final int iValue){
  if(null != iValue && 0 < iValue && 100 > iValue){
    this.iValue = iValue; // 
  }
  else{
    // do funny action because value is not valid
  }
}

or you do delegate this validation to another class(when pushing some "OK"-button) or even your textbox itself (write an extension and trigger on lost of focus or keystroke(can become strange if validation takes to long)).

regards,
Torsten

I never finish anyth...

Richard MacCutchan4-Jan-11 1:56

Re: Java MySQL Driver issue

4-Jan-11 1:56

pancakeleh wrote:
i tried google however have no clue on how to strt.

I already gave you a link to the Java tutorials. I suggest you spend some more time going through them, especially the areas that you are having difficulty with.

Just say 'NO' to evaluated arguments for diadic functions! Ash

Java MySQL Driver issue

khurram_shahzad29-Dec-10 6:03

khurram_shahzad

29-Dec-10 6:03

Hi, i am trying to connect to MySQL database mysql using JAVA .. using code given below,

import java.sql.*;

public class dbExample{
  public static void main(String[] args) {
    System.out.println("Listing all table name in Database!");
    Connection con = null;
    String url = "jdbc:mysql://localhost:3306/";
    String db = "mydb";
    String driver = "com.mysql.jdbc.Driver";
    String user = "root";
    String pass = "root";
    try{
      Class.forName(driver);
      con = DriverManager.getConnection(url+db, user, pass);
    }
    catch (Exception e){
      e.printStackTrace();
    }
  }
}

I've picked this example from internet .. and there lot more example i tried using this same driver String driver = "com.mysql.jdbc.Driver"; But this code all other i tried gives me error Driver Class not found ... at this statment Class.forName(driver); ..... and similarly on trying this driver sun.jdbc.odbc.JdbcOdbcDriver the above mentioned statment Class.fonName ... executes but then it gives error on statment con = DriverManager.getConnection(url+db, user, pass); error is No suitable drive found for jdbc:mysql://localhost:3306/mydb

I'm very much confused and tried it toooooo many time in diffrents ways that i could but still unable to create successfull database connection.
I've tried this using notepad / Netbeans both and both on WINDOWS7 and XP ... and both give same error to me .... Frown | :(

Please Please PLease give me any solution .... I shell be very very Thanksfull to you.

Min.Liao29-Dec-10 14:44

Min.Liao

29-Dec-10 14:44

your code is absolutely right，but if you use "com.mysql.jdbc.Driver", you should add jdbc driver for mysql in your lib.

download jdbc driver jar here:
http://dev.mysql.com/downloads/connector/j/

Re: Java MySQL Driver issue

khurram_shahzad29-Dec-10 20:30

khurram_shahzad

29-Dec-10 20:30

Ok Thanks you ver much ....... Problem solved by adding MySQL.jar to Library.
THanks a lot ...

java.lang.IllegalArgumentException

pancakeleh28-Dec-10 16:59

28-Dec-10 16:59

i have added a delete button on the table that i have created to allow user to delete values straight from the table and the database will then be updated. however when i try to run the program an error incurred.

Error: java.lang.IllegalArgumentException: unrecognized virtual form name: addIncidentStatus

my code as follows:

public String Del_btn_action() {

     form1.discardSubmittedValues("addIncidentStatus");
     try {

         RowKey rk = tableRowGroup1.getRowKey();
         if (rk != null) {

           incidentStatusDataProvider.removeRow(rk);
            incidentStatusDataProvider.commitChanges();
             incidentStatusDataProvider.refresh();}

     } catch (Exception ex) {

         log("ErrorDescription", ex);
         error(ex.getMessage());
     }
     return null;
 }

By the way the "addIncidentStatus" is a function in the sessionbean.

May i know what went wrong?

Problem

pancakeleh27-Dec-10 19:52

27-Dec-10 19:52

Hello i have no idea if i should post it at the java forum pr the database forum, pardon me if i post it at the wrong forum. i am currently using netbeans, javadb and glassfish for my project and right now i created a table that allow user to insert values into the database.

The table contains of 2 attributes a ID and Name.

Problem : http://img827.imageshack.us/img827/673/helpnb.png[^][^]

when the user try to add a 24 again as the ID an error page will popup. how do i create a message instead of the error popup?

error popup page : http://img824.imageshack.us/img824/1426/errorye.png[^]

Needing help.

Re: Problem

Richard MacCutchan27-Dec-10 22:31

27-Dec-10 22:31

pancakeleh wrote:
how do i create a message instead of the error popup?

Catch the exception[^] and deal with it.

Just say 'NO' to evaluated arguments for diadic functions! Ash

Re: Problem

RaviRanjanKr14-Apr-11 6:00

RaviRanjanKr

14-Apr-11 6:00

You need to handle the exception and then display your customize message box as your requirement.
take a look there[^] for getting more details about Exception.

convert to integer?

pancakeleh22-Dec-10 20:44