Threads in Java: Newbie question

Hi
I had a doubt regarding Threads. I have implemented a Security Manager which does not allow a thread to write into a file. Now, the problem is when the thread tries to write into a file, the Security Manager calls my function in which I want to immediately terminate the thread. How do i do this? How do I terminate a thread without using the deprecated Stop() function ?
Thanks in advance
RG

The trick is to make the thread die a natural death... One method is have a boolean somewhere which is initially set to true (maybe call it keepRunning?), and the thread that should die have a while loop which periodically checks to see that this boolean is still true.
The function which should terminate the thread can now set that variable to false and force the thread to die at the next iteration of its while loop.
There are more examples, more methods, and probably a better explanation at:
http://java.sun.com/docs/books/tutorial/essential/threads/lifecycle.html
Good luck!

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RFCLIB access from Perl / Java - newbie question

Hi folks,
I am newbie with SAP. I am triying to access the SAP from my web application, wrote in PErl or JAva.
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1) What software I need to install in my client side (the web server that host my web application)??
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Hi,
download the SAP JAVA Connector (SAP JCO) from
service.sap.com
There are enough examples for java.
Best Regards
Frank

Java Newbie Question - the import statement

Hi Geeks,
I have a problem for importing a java .class in my project. This latter is named "Tedetis_New". Inside it, I created a "src" folder containing all the source code of the application. I import a jar file inside the parent directory of "src" (i.e. at the root of the project). Inside this jar archive, two classes (.class files) are not placed inside a package (default package according to eclipse), let's name one toto.class. So when I want to import toto.class from a file inside the src directory I simply do "import toto.class" but this statement doesn't work ! I don't manage to import my toto.class so ... what do you propose for this ?
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Don't use the "default" class for anything serious;
you can't import such a class.Er, package maybe?Yes, I was editing my reply while you replied to my reply so I couldn't
edit my little blooper in my reply anymore; thank you very much Sir ;-)
kind regards,
JosI entered that response as quickly as I could, for just that reason. I
thought you might notice and try to correct it, and I wanted to preserve
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Everyone gather round and taunt Jos! Wave your private parts at his
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Java newbie questions...Setting the classpath in Unix

When you set the classpath, how do you include anything already in the classpath? For instance, if your profile sets your classpath to
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export classpath=~:MyJar.jar
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In csh, the CLASSPATH environment variable is modified with the setenv command. The format is:
setenv CLASSPATH path1:path2
In sh, the CLASSPATH environment variable can be modified with these commands:
CLASSPATH = path1:path2:...
export CLASSPATH
====
(From the Sun documentation)
or, in sh,
export CLASSPATH=path1:path2
should work

Visio like object drawing in Java - newbie question

Hi all,
Although a reasonably experienced java programmer I am new to the world of 2D graphics.
I am contemplating writing a tool which includes a diagramming capability for displaying computer systems and interactions between them.
I guess this would not be a million miles from what a UML diagramming tool does, but it would definitely have some differences.
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wpafbuser1 wrote:
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^1^ http://www.jgraph.com/

Another java newbie question: "Link errors"

In the environments I've attempted compiling in, it seems that there is a just-in-time default, which means that any missing classes are not found until run time.
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Java has no .h files, so it shouldn't compile at all if a class is missing, unless:
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They give you Library
You compile, javac sees theat "Library" exists and checks no further
At run time, you get errors about Library needs missing class "Extension"
What class is missing anyhow?

Java newbie question

Hi,
I have the following code:
public class Dice {
public static void main(String []arg){
Scanner scan = new Scanner(System.in);
Random ran = new Random();
public void RollDice(){
     ran.nextInt();
public int returnDice(){
     return ran.nextInt();
}And the compiler yells at me that it can't find the symbol variable ran.
If you create an instance of Dice how would you call it in the methods?

Gimli wrote:
Hi,
I have the following code:
And the compiler yells at me that it can't find the symbol variable ran.
If you create an instance of Dice how would you call it in the methods?
public class Dice {
private Scanner scan;
private Random ran;
public Dice() {
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    ran = new Random();
public static void main(String []arg) {
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    dice.RollDice();
    dice.returnDice();
public void RollDice() {
    ran.nextInt();
public int returnDice() {
    return ran.nextInt();
}OR
public class Dice {
public static void main(String []arg) {
    RollDice(new Random());
    System.out.println(returnDice(new Random()));
public static void RollDice(Random ran) {
    ran.nextInt();
public int returnDice(Random ran) {
    return ran.nextInt();
}Just a few ideas to think about.

Importing Java Class Question

Hello,
Sorry for such a newbie question and such a long post, I did remember how to do this before but now I can't for the life of me remember. Anyhow, I have a simple question about importing custom-made java classes, from another directory in the windows operating system. I have the classpath set, and also I realize that because the two files below are in the same directory theres no need for an import statement as Java will look for the class in the same directory.
But I would like to know how the import statement is suppose to look to import a custom made java class from another directory, (assuming of course that I set the correct classpath)
here's the java class location:
c:\school\csc365\narcus.java
//narcus.java
import java.io.*;
class narcus implements Comparable
String firstName = "firstName";
String lastName = "lastName";
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     lastName = lastName;
     public narcus(String f)
     firstName = f;
     lastName = lastName;
     public narcus(String f, String l)
     firstName = f;
     lastName = l;
public String getFirst()
return "first..";
     public int compareTo(Object e)
     return 1;
Here's the location of the driver program thats suppose to use the narcus.java class
c:\school\csc365\test.java
//test.java
//import statement? maybe import "c:\\school\\csc365\\*"; ?
import java.io.*;
class test
public static void main(String[] args)
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And also, here is my classpath:
PATH=c:\school\csc365\;c:\school\
The classpath also points to the jdk libraries and few other directories but I didn't write that above, as it probably isn't relevant.
I've tried the following import statements.
import "c:\\school\csc365\\narcus.java";
import "narcus.java";
import "c:\\school\\csc365\\*";
But I keep getting an error that says:
test.java:1 <identifier> expected
Any help is appreciated!

Hi Folks,
I am new to this forum, heard that interesting discussions always happens on this forum so immediately registered,don't want to miss any oppurtunity to participate in discussions.
I have pretty much basic question regarding compiling and exceuting files in different packages.I have the following directory structure
C:\Projects\WDPROEast\Development\CommonService\Code\Java from where java files stored in different packages as follows:
com\wdpro\commerce\common\crm\dae\nautilus\adapter directory has java files in com.wdpro.commerce.coomon.crm.dae.nautilus.adapter package.
com\wdpro\commerce\common\dae\exception has java files with package named com.wdpro.commerce.common.dae.exception.
com\wdpro\commerce\common\dls\exception has java files with corresponding package name.
com\wdpro\commerce\common\dto has java files under proper package name.
com\wdpro\commerce\common\exception has java files with appropriate package name.
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so I issued command for compilation as follows C:\Projects\WDPROEast\Development\CommonService\Code\Java>javac com/wdpro/commerce/common/crm/dae/nautilus/ada
pter/a.java com/wdpro/commerce/common/crm/dae/nautilus/adapter/NautilusServiceUtility.java com/wdp
ro/commerce/common/crm/dae/nautilus/adapter/URLReader.java com/wdpro/commerce/common/crm/dae/nautilus/adapter/
b.java com/wdpro/commerce/common/dae/exception/*.java com/wdpro/commerce/common/dto/*.java
com/wdpro/commerce/common/exception/*.java com/wdpro/commerce/common/util/*.java com/wdpro/commerce/common/dl
s/exception/*.java It compiled greatly but when I issue command to run a.class file as
C:\Projects\WDPROEast\Development\CommonService\Code\Java>java com/wdpro/commerce/common/crm/dae/nautilus/adap
ter/UtilityAccesssit's giving following exception
Exception in thread "main" java.lang.NoClassDefFoundError: com/wdpro/commerce/common/crm/dae/nautilus/adapter/
UtilityAccesssbut when I run a.java with the following command
C:\Projects\WDPROEast\Development\CommonService\Code\Java>java com/wdpro/commerce/common/crm/dae/nautilus/adap
ter/UtilityAccess com/wdpro/commerce/common/crm/dae/nautilus/adapter/NautilusServiceUtility.java com/wdpro/com
merce/common/crm/dae/nautilus/adapter/URLReader.java com/wdpro/commerce/common/crm/dae/nautilus/adapter/Nautil
usAccessUtility.java com/wdpro/commerce/common/dae/exception/*.java com/wdpro/commerce/common/dto/*.java com/w
dpro/commerce/common/exception/*.java com/wdpro/commerce/common/util/*.java com/wdpro/commerce/common/dls/exce
ption/*.javaSo my question do I need to add all required java files to path when required class files are under different packages?is it manadatory.
I hope you understand my question,pass me any comments you may have.
Thanks alot,
Anu

Help with "Exception in thread "Thread-4" java.lang.NullPointerException"

I am new to Java and I am trying a simple bouncing ball example from Stanford. Here is their simple example that works.
import acm.program.*;
import acm.graphics.*;
import java.awt.*;
public class BouncingBallWorking extends GraphicsProgram {
/** sets diameter */
private static final int DIAM_BALL = 30;
/** amount y velocity is increased each cycle */
private static final double GRAVITY = 3;
/** Animation delay or pause time between ball moves */
private static final int DELAY = 50;
/** Initial X and Y location ball*/
private static final double X_START = DIAM_BALL / 2;
private static final double Y_START = 100;
private static final double X_VEL = 3;
private static final double BOUNCE_REDUCE = 0.9;
private double xVel = X_VEL;
private double yVel = 0.0;
private GOval BallA;
public void run() {
setup(X_START,Y_START);
//         Simulation ends when ball goes off right hand
//         end of screen
while (BallA.getX() < getWidth()) {
moveBall(BallA);
checkForCollision(BallA);
pause(DELAY);
private void setup(double X_coor, double Y_coor) {
BallA = new GOval(X_coor, Y_coor, DIAM_BALL, DIAM_BALL);
add(BallA);
private void moveBall(GOval BallObject) {
yVel += GRAVITY;
BallObject.move(xVel,yVel);
private void checkForCollision(GOval BallObject) {
if(BallObject.getY() > getHeight() - DIAM_BALL){
yVel = - yVel * BOUNCE_REDUCE;
double diff = BallObject.getY() - (getHeight() - DIAM_BALL);
BallObject.move(0, -2 * diff);
} Now I am trying to modify "setup" so it I can create several balls. I made a simple modification to "setup" and now I am getting an error.
"Exception in thread "Thread-4" java.lang.NullPointerException
at BouncingBallNotWorking.run(BouncingBallNotWorking.java:36)
at acm.program.Program.runHook(Program.java:1592)
at acm.program.Program.startRun(Program.java:1581)
at acm.program.AppletStarter.run(Program.java:1939)
at java.lang.Thread.run(Unknown Source)"
Can you describe why I am getting an error? Thanks.
Here is what I changed.
Before:
     private void setup(double X_coor, double Y_coor) {
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     }After:
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          BallObject = new GOval(X_coor, Y_coor, DIAM_BALL, DIAM_BALL);
          add(BallObject);
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* File:BouncingBall.java
* This program graphically simulates a bouncing ball
import acm.program.*;
import acm.graphics.*;
import java.awt.*;
public class BouncingBallNotWorking extends GraphicsProgram {
/** sets diameter */
private static final int DIAM_BALL = 30;
/** amount y velocity is increased each cycle */
private static final double GRAVITY = 3;
/** Animation delay or pause time between ball moves */
private static final int DELAY = 50;
/** Initial X and Y location ball*/
private static final double X_START = DIAM_BALL / 2;
private static final double Y_START = 100;
private static final double X_VEL = 3;
private static final double BOUNCE_REDUCE = 0.9;
private double xVel = X_VEL;
private double yVel = 0.0;
private GOval BallA;
public void run() {
setup(X_START,Y_START, BallA);
//         Simulation ends when ball goes off right hand
//         end of screen
while (BallA.getX() < getWidth()) {
moveBall(BallA);
checkForCollision(BallA);
pause(DELAY);
private void setup(double X_coor, double Y_coor, GOval BallObject) {
BallObject = new GOval(X_coor, Y_coor, DIAM_BALL, DIAM_BALL);
add(BallObject);
private void moveBall(GOval BallObject) {
yVel += GRAVITY;
BallObject.move(xVel,yVel);
private void checkForCollision(GOval BallObject) {
if(BallObject.getY() > getHeight() - DIAM_BALL){
yVel = - yVel * BOUNCE_REDUCE;
double diff = BallObject.getY() - (getHeight() - DIAM_BALL);
BallObject.move(0, -2 * diff);
} Edited by: TiredRyan on Mar 19, 2010 1:47 AM

TiredRyan wrote:
That is great! Thanks. I've got two question though.
1.) Now I want to have 100 bouncing balls. Is the best way to achieve this is through an array of GOvals? I haven't gotten to the lecture on arrays on Stanford's ITunesU site yet so I am not sure what is possible with what I know now.An array would work, or a List. But it doesn't matter much in this case.
2.) Are references being passed by value only applicable to Java or is that common to object-oriented programming? Also is there a way to force Java to pass in "BallA" instead of the value "null"?I can't say about all OO languages as a whole, but at least C++ can pass by reference.
And no, there's no way to pass a reference to the BallA variable, so the method would initialize it and it wouldn't be null anymore.
When you call the method with your BallA variable, the value of the variable is examined and it's passed to the method. So you can't pass the name of a variable where you'd want to store some object you created in the method.
But you don't need to either, so there's no harm done.

J2ee server Exception in thread Main java.lang.OutOfMemoryError

hallo
i need your help
first my java j2ee and jdk
j2ee j2sdkee1.3.1
jdk j2sdk 1.4
i nedd the server for jms.
when i started the server with j2ee -verbose
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Starting web service at port: 8000
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i read in this forum about -Xms und Xmx but this Commands don't go on my system.
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Hi Warren,
Still I am not clear with your question. But generally this out of memoryspace error can be rectified by changing the properties which comes in the menubar of your command prompt. Then increasing the virtual memory over there. I hope this will help you.
Thanks
Bakrudeen
Technical Support Engineer
Sun MicroSystems Inc, India

Exception in thread "main" java.lang.NoClassDefFoundError: oracle/xml/parser/v2/

Hi!
Kindly assist on the following error.
I'm doing the sample acmevideo on Cashier Application deploying as a Java Application from JDeveloper3.0 and Oracle8i 8.1.5. And I had this error after executing the following command;
Path=e:\javaWebServer2.0\jre\bin;%Path%
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oracle/xml/parser/v2/DOMParser
at
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at oracle.dacf.dataset.SessionInfo.publishSession(SessionInfo.java:952)
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Make sure the classpath for the application includes all necessary dependency archives.
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How to solve this problem"exception in thread "main" java.lang.noclassdeff"

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public class hello
public static void main (String args[])
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anyone can help me ,thank you!
i am a student in China,it's a hard time for me to write down my question in english ,i doubt whether i express my question clearly.
thank you for you reading.

I have created a simple applet.
import java.lang.*;
import java.awt.*;
public class jawtex3 extends java.applet.Applet
public void init()
add(new Button("One"));
add(new Button("Two"));
public Dimension preferredSize()
return new Dimension(200, 100);
public static void main(String [] args)
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thankyou.

V basic newbie question

hi i had decided this weekend to start looking at the JAVA stuff I should be a real help to me at work. However i am having a problem setting things up. i have looked at the FAQ's but they don't seem to answer my question which is HOW do I set my computer up?
I'm running win98 java 1.4.3
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I took all the suggested options when the SDK was installing ans set the path but still can't get this one sorted.
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When running the program don't add the file extension .java.
The .java is only for source files not compiled yet.
After you compile you run them by just indicating the class name
java ExampleProgram

Java newbie help (type casting, 64bit unsigned Long)

Hi I am java newbie and need help on my project. I have a few questions. Can you put strings in a hashtable and test for their being their with the appropriate hashtable method? I want to test for equal strings, not the same object. Second question can you use all 64 bits of an unsigned long? java doesn't seem to allow this. Any packages that do?
Thanks,
Dave

Try casting it to Long instead of long. Long (capital L) is an Object, while long (lower case l) is not. You may also check to make sure the value isn't null. I would have thought that autoboxing would have worked here unless the value was null. But I am no expert on autoboxing.
Edit >> Checking for null ain't a bad idea but has nothing to do with the problem - this is a compile time problem. Sorry.
Also>> This code should work:
long cTime=(Long)session.getAttribute("creationtime");Edited by: stevejluke on Jul 1, 2008 11:00 AM

Domain Name settings in Solaris - Newbie question

Sorry for a newbie question!
I am already pointing a domain name to web hosting for email account. Now, I need an application server to run ERP software and Oracle, and installing Solaris and Oracle need a domain name.
If I point my domain name to the server, how do I receive emails from web hosting???
Install an email server to the application server instead? What can I do if I want the same domain name?

Your questions are completely off-topic for the forum.
These SunOS forums are for questions on <i>"how do I install my OS"</i>
You particular question is in the <i>"how can I install Solaris while using the CD drive"</i> forum.
So, if you had a question on how to edit the /etc/inet/hosts file to establish a FQDN on the computer, then it might be appropriate for the forum.
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