Call a method of a class file from an Applet

I have an Applet nmaed CountDown.java in which I have to call a method "doSelect" of a class file named DBConnection.java. How do I do this? Both the Applet and the class file are in the same directory.

You should put both classes in the same package and create a jar file containing the whole package.
Make sure the DBConnection class is public or protected and that the method you're trying to call is public or protected.

Similar Messages

Calling a method in a class extended from thread

I'm trying to use two threads of type ThreadTest to call the addNum method in the class below. I found that i couldnt call the addnum method with the instances I created but had to make the addnum method static and then call it with the class name ThreadTest.Is there anyway to get round this? i'm doing this exercise to try and understand synchronisation. Thanks
import java.lang.Thread;
import java.util.*;
class ThreadTest extends Thread implements Runnable{
     private int x;
     private static ArrayList intnumbers = new ArrayList();
     public ThreadTest(int no)
          x=no;
     public void run()
          for (int i=0; i<x; i++)
               try
               System.out.println(i);
               Thread.currentThread().sleep((long)(Math.random() * 1000));
          }catch(InterruptedException e ){e.getMessage();}
     public static void addNum(int n)
          synchronized(intnumbers){
                    intnumbers.add(new Integer(n));
public static void main(String[] args)
     Thread testThread = new Thread(new ThreadTest(50));
     Thread testThreadb = new Thread(new ThreadTest(50));
     testThread.start();
     testThreadb.start();
          ThreadTest.addNum(10);
    //*** this gives an error
    //testThread.addNumber(10);
    //testThreadb.addNumber(10);
}

ok here goes again. ;).
import java.lang.Thread;
import java.util.*;
class ThreadTest extends Thread implements Runnable{
     private int x;
     private static ArrayList intnumbers = new ArrayList();
     public ThreadTest(int no)
          x=no;
     public void run()
          for (int i=0; i<x; i++)
               try
               System.out.println(i);
               Thread.currentThread().sleep((long)(Math.random() * 1000));
          }catch(InterruptedException e ){e.getMessage();}
     public static void addNum(int n)
          synchronized(intnumbers){
                    intnumbers.add(new Integer(n));
public static void main(String[] args)
     Thread testThread = new ThreadTest(50);
     testThread.start();
     //gives error so how can i create 2 instances of testThread and call addNum with them?
     //testThread.addNum(10);
//works ok but I want to call addNum with 2 different threads
     ThreadTest.addNum(10);
}

Calling a method of one class from another withing the same package

hi,
i've some problem in calling a method of one class from another class within the same package.
for eg. if in Package mypack. i'm having 2 files, f1 and f2. i would like to call a method of f2 from f1(f1 is a servlet) . i donno exactly how to instantiate the object for f2. can anybody please help me in this regard.
Thank u in advance.
Regards,
Fazli

This is what my exact problem.
i've created a bean (DataBean) to access the database. i'm having a servlet program (ShopBook). now to check some details over there in the database from the servlet i'm in need to use a method in the DataBean.
both ShopBook.java and DataBean.java lies in the package shoppack.
in ShopBook i tried to instantiate the object to DataBean as
DataBean db = new DataBean();
it shows the compiler error, unable to resolve symbol DataBean.
note:
first i compiled DataBean.java, it got compiled perfectly and the class file resides inside the shoppack.
when i'm trying to compile the ShopBook its telling this error.
hope i'm clear in explaining my problem. can u please help me?
thank u in advance.
regards,
Fazli

How to call class file from jsp without creating packages

i m using tomcat 5.5
i stored my class file into WEB-INF\Class directory
how to call that class file. from my jsp page.
i got some error.
i used package concept,that works fine.

i m using tomcat 5.5
i stored my class file into WEB-INF\Class directory
how to call that class file. from my jsp page.
i got some error.
i used package concept,that works fine.Then use packages.
As of Java1.4, you can no longer import classes from the default package (no package declared) into classes that are packaged.
All Tomcat classes are in packages, including the compiled JSP.
Therefore: Your classes need to be in a package inorder to be imported and used by the JSP.
Why the problem? If you know it works with packages, why try not to use them?

How to call a method of another class ?

Hello,
I�d like to know how to call a method of another class. I have to classes (class 1 and class 2), class 1 instantiates an object of class 2 and executes the rest of the method. Later, class 1 has to call a method of class 2, sending a message to do something in the object... Does anybody know how to do that ? Do I have to use interface ? Could you please help me ?
Thanks.
Bruno.

Hi Schiller,
The codes are the following:
COMECO
import javax.swing.UIManager;
import java.awt.*;
import java.net.*;
import java.io.*;
import java.awt.event.*;
import javax.swing.*;
//Main method
class comeco {
public static void main(String[] args) {
try {
UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
catch(Exception e) {
AGORA testeagora=new AGORA();
// Code for socket
int port;
     ServerSocket server_socket;
     BufferedReader input;
     try {
     port = Integer.parseInt(args[0]);
     catch (Exception e) {
     System.out.println("comeco ---> port = 1500 (default)");
     port = 1500;
     try {
     server_socket = new ServerSocket(port);
     System.out.println("comeco ---> Server waiting for client on port " +
               server_socket.getLocalPort());
     // server infinite loop
     while(true) {
          Socket socket = server_socket.accept();
          System.out.println("comeco ---> New connection accepted " +
                    socket.getInetAddress() +
                    ":" + socket.getPort());
          input = new BufferedReader(new InputStreamReader(socket.getInputStream()));
          // print received data
          try {
          while(true) {
               String message = input.readLine();
               if (message==null) break;
               System.out.println("comeco ---> " + message);
testeagora.teste(message);
          catch (IOException e) {
          System.out.println(e);
          // connection closed by client
          try {
          socket.close();
          System.out.println("Connection closed by client");
          catch (IOException e) {
          System.out.println(e);
     catch (IOException e) {
     System.out.println(e);
AGORA
import javax.swing.UIManager;
import java.awt.*;
import java.awt.event.*;
import java.net.*;
import java.io.*;
import javax.swing.*;
import java.net.*;
//public class AGORA {
public class AGORA {
boolean packFrame = false;
//Construct the application
public AGORA() {
try {
Main frame = new Main();
System.out.println("agora ---> Criou o frame");
//Validate frames that have preset sizes
//Pack frames that have useful preferred size info, e.g. from their layout
if (packFrame)
frame.pack();
else
frame.validate();
//Center the window
Dimension screenSize = Toolkit.getDefaultToolkit().getScreenSize();
Dimension frameSize = frame.getSize();
if (frameSize.height > screenSize.height)
frameSize.height = screenSize.height;
if (frameSize.width > screenSize.width)
frameSize.width = screenSize.width;
frame.setLocation((screenSize.width - frameSize.width) / 2, (screenSize.height - frameSize.height) / 2);
frame.setVisible(true);
catch(Exception e)
{ System.out.println("agora ---> " +e);
// Tem que criar a THREAD e ver se funciona
public void remontar (final String msg) {
try {
               System.out.println("agora ---> Passou pelo Runnable");
System.out.println("agora --> Mensagem que veio do comeco para agora: "+ msg);
Main.acao(msg);
catch(Exception x) {
x.printStackTrace();
MAIN
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import com.borland.jbcl.layout.*;
import javax.swing.border.*;
import java.net.*;
import java.io.*;
public class Main extends JFrame {
// ALL THE CODE OF THE INTERFACE
//Construct the frame
public Main() {
enableEvents(AWTEvent.WINDOW_EVENT_MASK);
try {
jbInit();
catch(Exception e) {
e.printStackTrace();
public void acao() {
// C�digo para mudar a interface
Runnable setTextRun=new Runnable() {
public void run() {
try {
               System.out.println("main ---> Passou pelo Runnable");
TStatus.setText("main ---> Funcionou");
catch(Exception x) {
x.printStackTrace();
System.out.println("main ---> About to invokelater");
SwingUtilities.invokeLater(setTextRun);
System.out.println("main ---> Back from invokelater");
// Aqui vai entrar o m�todo para ouvir as portas sockets.
// Ele deve ouvir e caso haja alguma nova mensagem, trat�-la para
// alterar as vari�veis e redesenhar os pain�is
// Al�m disso, o bot�o de refresh deve aparecer ativo em vermelho
//Component initialization
private void jbInit() throws Exception {
// Initialize the interface
//Setting | Host action performed
public void SetHost_actionPerformed(ActionEvent e) {
     int port;
     ServerSocket server_socket;
     BufferedReader input;
System.out.println("main ---> port = 1500 (default)");
     port = 1500;
     try {
     server_socket = new ServerSocket(port);
     System.out.println("main ---> Server waiting for client on port " +
               server_socket.getLocalPort());
     // server infinite loop
while(true) {
          Socket socket = server_socket.accept();
          System.out.println("main ---> New connection accepted " +
                    socket.getInetAddress() +
                    ":" + socket.getPort());
          input = new BufferedReader(new InputStreamReader(socket.getInputStream()));
String espaco=new String(": ");
     JLabel teste2=new JLabel(new ImageIcon("host.gif"));
          PHost.add(teste2);
System.out.println("main ---> Adicionou host na interface");
          repaint();
System.out.println("main ---> Redesenhou a interface");
          setVisible(true);
          // print received data
          try {
          while(true) {
               String message = input.readLine();
               if (message==null) break;
               System.out.println("main ---> " + message);
          catch (IOException e2) {
          System.out.println(e2);
          // connection closed by client
          try {
          socket.close();
          System.out.println("main ---> Connection closed by client");
          catch (IOException e3) {
          System.out.println(e3);
     catch (IOException e1) {
     System.out.println(e1);
public void OutHost_actionPerformed(ActionEvent e) {
          repaint();
          setVisible(true);
//Help | About action performed
public void helpAbout_actionPerformed(ActionEvent e) {
Main_AboutBox dlg = new Main_AboutBox(this);
Dimension dlgSize = dlg.getPreferredSize();
Dimension frmSize = getSize();
Point loc = getLocation();
dlg.setLocation((frmSize.width - dlgSize.width) / 2 + loc.x, (frmSize.height - dlgSize.height) / 2 + loc.y);
dlg.setModal(true);
dlg.show();
//Overridden so we can exit on System Close
protected void processWindowEvent(WindowEvent e) {
super.processWindowEvent(e);
if(e.getID() == WindowEvent.WINDOW_CLOSING) {
fileExit_actionPerformed(null);
public void result(final String msg) {
// C�digo para mudar a interface
Runnable setTextRun=new Runnable() {
public void run() {
try {
               System.out.println("main ---> Chamou o m�todo result para mudar a interface");
System.out.println("main --> Mensagem que veio do agora para main: "+ msg);
TStatus.setText(msg);
catch(Exception x) {
x.printStackTrace();
System.out.println("main --> About to invokelater");
SwingUtilities.invokeLater(setTextRun);
System.out.println("main --> Back from invokelater");
[]�s.

Why do I get multiple class files from 1 java file?

I wrote a dialog box using gridBagConstraints and another program RunPanel to run it as a java application. For the first time since playing with java, I get multiple class files from a single java file.
This seems very strange to me and wonder if anyone else has come across this and what could possibly be the reason for it. I did a clean (in Eclipse) just to make sure it wasn't garbage and sure enough they come back again.
I have ReconPanel.java from which I get ReconPanel.class with the addition of ReconPanel$N.class where N goes from 1 to 5.
The same thing in RunPanel but here there is only 1 extra file, RunPanel$1.class.
I'll include the code for RunPanel since it is relatively small:
package ilan;
import javax.swing.JFrame;
public class RunPanel extends JFrame {
     private static final long serialVersionUID = 1L;
     private ReconPanel m_reconPanel = null;
     public RunPanel() {
          super();
          initialize();
      * This method initializes this
     private void initialize() {
        this.setTitle("tester");
        this.setSize(new java.awt.Dimension(138,396));
        this.addWindowListener(new java.awt.event.WindowAdapter() {
             public void windowClosing(java.awt.event.WindowEvent e) {
                  m_reconPanel.exitPanel();
                  System.exit(0);
          m_reconPanel = new ReconPanel();
          this.getContentPane().add(m_reconPanel);
      * @param args
     public static void main(String[] args) {
          JFrame frame1 = new RunPanel();
          frame1.setVisible(true);
} // @jve:decl-index=0:visual-constraint="10,10"The only thing "unusual" I do is to put a listener on the WindowClosing so that I can go back to ReconPanel and write results to the registry.
Can anyone tell me what is going on?
Thanks,
Ilan

He IIan,
Yes, you get number of extra class files based on your number of anomyous class es used. Like in your RunPanel, you get only 1 ..$1.class file, b'coz u have used only 1 annomyous class & i.e WindowAdapter. Take a look at this code :-
this.addWindowListener(new java.awt.event.WindowAdapter() {
             public void windowClosing(java.awt.event.WindowEvent e) {
                  m_reconPanel.exitPanel();
                  System.exit(0);
        });Similarly, in your ReconPanel, you must have used such kind of classes 5 times, & hence u get such 5 extra classes. To avoiod such extra classes, if you can directly implement that interface or extend the class, if possible will be best. For example, for each button, u write
button1.addActionListener(new ActionListener() {
// Code
});Instead, of this, its better to implement ActionListener & write
button1.addActionListener(this);
public void actionPerformed(ActionEvent ae) {
   if (ae.getSource() == button1) {
   // CODE
   }Likethis, you can get rid of such numerous extra class files. In IDE, if you ask to add actionEvent, it will do the first method. To get rid of it, don't add event in the properties, instead, apply the second method. The same thing applies for anyother event. The first option is worthful, if by implementing, u got to write 5 functions from which u r gonna use just 1 method.
Hope this clears your question.
Trupti

How to call java method having array as argument from c++ ?

Hello sir,
how to call java method having array as arguments from c++;
here is java code which is called from c++
class PQR {
     public void xyz(int[] ia) {
     System.out.println("hi");
          for (int i = 0; i < ia.length; i++)
               System.out.println(ia);
suppose all jvm invocation is done...

For someone well versed in java, C++ and JNI although tedious that should be obvious.
For someone not well versed in all three it is going to be very difficult.
Even for someone that does have knowledge in all of those areas coming up with a C++ interface that reflects that functionality in a dynamic way such that anyone is will to use it is going to be quite an adventure.
At any rate to start building it you do exactly the same thing that you would in java.
1. Extract everything in the jar via the zip package
2. For each found instance extract all of the methods, return types, parameters, etc and build a description tree for each class.
Doing all of that in C++ is going to take a LOT of code. If someone wanted an estimate from me it would take me 6 months to do it. And before I would even attempt it I would get them to explain to me in detail exactly how they thought they were going to use it when I was done because I can't see any reasonable way to do that.
I left out the description tree itself. I suppose you could duplicate the entire reflection api in C++.
Now perhaps if it was much, much more constrained, like to only those classes that implement a single interface then that would be more reasonable.

Executing class files from a Java App dynamically

Hi!, Is there any way i can execute java .class files from my Java Application dynamically. I know that java uses Dynamic method Invocation. Is that true of class files generated using some other language compiled for the JVM.
In my case i would like to make a Web browser that interprets HTML and also java applets embeded in them. I would like to use the JRE of the platform execute the applets for me rather than writing the code for my Browser to interpret the class files.
Thanks in Advance.

You just need a custom class loader to bring these applets into your JVM.
http://developer.java.sun.com/developer/onlineTraining/Security/Fundamentals/magercises/URLClassLoader/index.html
Then you can use the methods of java.lang.Class to create an instance of such a class. As soon as you have it, you can just treat it as a regular Applet and invoke init(), stop() etc. appropriately.
If you want to execute anything else than conventional Applets, you might consider reflection to find out about methods implemented:
http://java.sun.com/docs/books/tutorial/reflect/index.html

Calling a method in the view controller from the component controller

Hi
Is there anyway to call a method in the view implementation from the component controller??
Thanks
jack

Thanks for all your replies. I want this kind of a functionality because Im trying to invove a DC (Child DC) from a Parent DC such that the Child DC's view is displayed onto the view container of the Parent DC. I have embedded using 'interface view of a component instance' in the Parent Window and am able to create the component and set usage though the onPlugDefault of the Child View.
But I observe that when i make a call from the parent, the flow is like this:
1. The wdDoInit of the Child Component Controller gets triggered first.
2. Then the wdDoInit of the Child's <b>VIEW</b> gets triggered
3. and <b>THEN</b> the onPlugDefault of the Child Component Interface View
What I had actually wanted was to Fire onPlugDefault where Im calling a method LoadData(), after which the Child DC's view must be triggered so it can display the fetched data.
What is actually happening is the view gets displayed, but no data is displayed in the view.
Right now I have just given a work around where Im triggering <b>LoadData()</b> of the <b>COmponent COntroller</b> from the <b>wdDoInit</b> of the <b>VIEW</b>.
Is there a better way to do this? I find it strange that I have to load the Data from the view.
Thanks
Jack

Calling a Method in other Class

I want to call a method in another class when an action is preformed can anyone suggest how I might do this??
     addSquare.addActionListener(new ActionListener()
               public void actionPerformed(ActionEvent e)


I want to call a method in another class when an
action is preformed can anyone suggest how I might do
this??
        addSquare.addActionListener(new ActionListener()
             public void actionPerformed(ActionEvent e)
             {               OtherClass oc = //getrefererncetootherclass
               oc.methodtocall(params, to, pass);

How to restrict the .class file from decompilation

Hi all,
i got a security problem. i need all the java class files to be most secured. is there any to restriction on the java class files from decompilation. is that possible?. pls help me out. it's very urgent
thanks in advance

You can make it harder to understand the decompiled code if you use an obfuscator. (I don't have links to any, do a google search, or search these forums, it have been discussed here previously.)
You cannot completely prevent decompilation, though. Obfuscating does not for example not mean that any passwords you have hardcoded in the source is secure.

Running the .class file from java code

I'm doing a kind of providing service like compiling and running Java code on server side and giving output to the end user.
Please suggest me an approach with code to run .class file from the Java code.
import java.io.*;
public class demo {
public static void main(String args[]) throws IOException, InterruptedException {
int result;
try {
System.out.println("command output:");
Process proc = Runtime.getRuntime().exec("java -cp . demoh");
InputStream in = proc.getInputStream();
result = proc.waitFor();
BufferedInputStream buffer = new BufferedInputStream(proc.getInputStream());
BufferedReader commandOutput = new BufferedReader(new InputStreamReader(buffer));
String line = null;
System.out.print(commandOutput);
try {
while ((line = commandOutput.readLine()) != null) {
System.out.print(line);
System.out.println("command output: " + line);
}//end while
commandOutput.close();
} catch (IOException e) {
//log and/or handle it
}//end catc
} catch (IOException e) {
System.err.println("IOException raised: " + e.getMessage());
}

What happened when you tried what you have there?

Calling a method in Runnable Class

Hello I am trying to water this down but how can I call a method in my class
If I am passed only thread t.
MyClass mc = new MyClass();
Thread t = new Thread(mc);
t.start(); //works because it is a method of Thread
t.myMethodInMyClass (); // wont work because it cant find it
I have attempted casting to MyClass but I get CCException.
Any help would be wonderful..
cheers and thanks in advance.
Scott

Well, you could potentially have too many things in one class. You may want to try and modularize your classes more. But 'if in several situations [you] need different things to run'... well, the logic is just going to have to be there for that in some form.
Now, if you've already performed the logic to determine what to run and you are going to have to perform the logic again (in your run() method), then there is a flaw in your design.

Tomcat6 does not load class files from WEB-INF/lib/myjarfile.jar WHY???

I have placed my jar file in c:\tomcat6\webapps\my-application\WEB-INF\lib\myjarfile.jar
But, after restarting tomcat6, when i try to import the class file contained in the myjarfile.jar in a servlet, it says
ProcessFileUpload.java:4: package test.test1 does not exist
import test.test1.*;
^It clearly tomcat's class loading problem.
As i unzipped my jar and placed the packagefolder structure to
c:\tomcat6\webapps\my-application\WEB-INF\classes\testand it works perfectly.
Anyone knows its workaround? please suggest if any configuration changes is required in tomcat or so.
Thanks.
---Sujoy

Thank you gimbal2 . There was error in creating the jar file myjarfile.jar.
But, now I have created it again and placed it in place
c:\tomcat6\webapps\my-application\WEB-INF\lib\myjarfile.jarand tried to use one on the Class file included within the jar to compile my servlet. But, still I am getting error at servlet compilation time. I want to place executable jar files in
c:\tomcat6\webapps\my-application\WEB-INF\lib\myjarfile.jar and compile my servlet and execute the servlet.
I DO NOT WANT TO unzip the jar, placing all unzipped files to
c:\tomcat6\webapps\my-application\WEB-INF\classes\ folder and comiple my servlet and execute the servlet. But, I am failing to user WEB-INF\lib\ folder facility....please help me why i am not getting class files from WEB-INF\lib\ folder.
If you please see the small code bit and tell me any possible error that would be very helpful.
Step 1: my library java file MyClass.java
package test.test1;
public class MyClass {
     String myName = "Default return string value";
     public void setMyName(String varName) {
          this.myName = varName;
     public String getMyName() {
          return this.myName;
}Step2 : Creating jar file of my library class files
C:\jdk1.6\bin>jar cvf myjarfile.jar test
added manifest
adding: test/(in = 0) (out= 0)(stored 0%)
adding: test/test1/(in = 0) (out= 0)(stored 0%)
adding: test/test1/MyClass.class(in = 452) (out= 296)(deflated 34%)
adding: test/test1/MyClass.java(in = 230) (out= 140)(deflated 39%)
C:\jdk1.6\bin>Step3 : Double checking the created jar file content by listing its content
C:\jdk1.6\bin>jar tf myjarfile.jar
META-INF/
META-INF/MANIFEST.MF
test/
test/test1/
test/test1/MyClass.class
test/test1/MyClass.java
C:\jdk1.6\bin>Step4 : Placed myjarfile.jar to
c:\tomcat6\webapps\my-application\WEB-INF\lib\Step5 : Restarted standalone Tomcat6 in my Windows XP SP2.
Step6 : Created a simple servlet LibFolderTest.java within my-application\WEB-INF\classes\ folder with code
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
import test.test1.*;
public class LibFolderTest extends HttpServlet {
     public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
          response.setContentType("text/html");
          PrintWriter out = response.getWriter();
          MyClass mc = new MyClass();
          out.println(mc.getMyName());
}Step7 : Tried to compile my servlet LibFolderTest.java and got the following error
LibFolderTest.java:4: package test.test1 does not exist
import test.test1.*;
^
LibFolderTest.java:11: cannot find symbol
symbol : class MyClass
location: class LibFolderTest
                MyClass mc = new MyClass();
                ^
LibFolderTest.java:11: cannot find symbol
symbol : class MyClass
location: class LibFolderTest
                MyClass mc = new MyClass();
                                 ^
3 errorsThe above servlet compilation error on Step7 is telling me that myjarfile.jar is not loaded by Tomcat6 or not available for use when compiling servlet. I want to use myjarfile.jar from within WEB-INF\lib\ folder but I can not. please help.
---Sujoy

How to call a function in one .js file from another .js file

Hello Techies,
I am trying to call a function in two.js file from one.js file.
Here is my code
one.js
<script>
document.write("<script type='text/javascript' src='/htmls/js/two.js'> <\/script>");
     function one()
                    var a;
                   two(a);
          }two.js
              function two(a)
                      alert("two");
                  }But the function two() is not working.
How can I do this one??
regards,
Krish

I think there is a syntax error in line
document.write("<script type='text/javascript' src='/htmls/js/two.js'> <\/script>");
end tag <\/script> is wrong.

Call a method of a class file from an Applet

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