Guru question, class reloading, resolved symbols

How can I determine all of the class symbols that get
resolved in a java class file? I want this from java, the
utility javap doesn't really fit the bill since it doesn't
give me the information I want.
BACKGROUND
I'm creating a class reloader which loads many packages. In order to get the reloading effect, a new
class loader must be instantiated...which is fine. The usual approach is to reload every class on the class path, but this is too time consuming. I would like to
be more elegant and only reload the minimum set of class files and delegate appropriately.
In order to do this I need need to know all of the symbols used by a particular class. For example,
if a class ABC has a method that uses class XYZ, and
XYZ gets modified to be XYZ'. I need to reload ABC if
I reload XYZ', otherwise ABC will use XYZ. This is
behavior spec'ed in JVM class loader spec (5.3).
The JVM spec also outlines the format of the
class file, but I really don't want to parse this myself.
Are there any utilities to facilitate inspecting class
files and getting this kind of information.

The usual approach is to reload every class on the class path...Huh? I was rather certain that classes were loaded as needed, not as found.
I need to reload ABC if I reload XYZ', otherwise ABC will use XYZ.
This is behavior spec'ed in JVM class loader spec (5.3).I don't understand this either. You can't 'reload' XYZ. You can load a different class. Or you can use a different class loader and load the a class with the same name (although the jvm will treat it as a different class.) Or you can wait for the jvm to collect the class loader (which means no instances of XYZ at a minimum) and then load what ever you want. Reloading to me suggests that you are some how replacing the existing class and that can't happen.
If the only reference in ABC is a method (local and not static) then I don't believe the class will be loaded until the method is called.
Whatever class loader loaded ABC and XYZ will not be gc'd until there are no instances of the classes it loaded. So if both use the same class loader then by definition when you load ABC, when you get a chance to load XYZ you can do whatever you want.
So, given the above, I am not sure I understand the question.

Similar Messages

Visual Studio 2012 cannot resolve symbol or Errors control is not a member of class

Visual Studio 2012 Web Site Project (Note not a Web application, so there are not Designer.vb files) > Site works perfectly fine and using IIS and attaching to IIS to debug code.
However, if I try to build the site inside of Visual Studio I am getting lots of Errors ‘pnlName’ is not a member of ‘Page_Name’ In the code behind I am getting errors ‘Cannot resolve symbol ‘pnlName’
.ascx Page
<li style="margin-right:0;" id="pnlName" runat="server"><a href="/cart" title="Checkout" class="global-checkout">Checkout</a></li>
.ascx.vb page
Me.pnlName.Attributes.Remove("style")
I have cleaned, rebuild and nothing gets rid of these errors, but again the site works as designed, but I would like to launch and debug inside of Visual Studio.
Moojjoo MCP, MCTS
MCP Virtual Business Card
http://moojjoo.blogspot.com

Cor,
What I am stating is this is a solution using the Web Site Project instead of a
Web Application Project.
Web Site projects do not require Designer.vb files, Web Application Projects add Designer.vb files in the solution.
Background: I have been hired to support a very successful e-commerce site that was built by a 3rd party vendor (I had no input on the contract or specification, because I would have went with
MVC). The site works 100% correctly, however from my 2003 - 2015 experience with Visual Studio and Web Development being in Web Forms and MVC I have always built ASP.NET Solutions using the Web Application Project Templates, which compiles the code down
to .dlls.
A Web Site project does not compile the code, but simply uses the .vb files and they have to be migrated to the server with the .aspx files. http://msdn.microsoft.com/en-us/library/dd547590%28v=vs.110%29.aspx
Currently the only way I can debug this Solution is to attach to the w3wp.exe process running locally on my work station.
The Solution is comprised of two Web Sites, which I cannot get it to compile because of the following errors -
'webServerControlName' is not a member of '(Protected Code Behind Class Name)' I am reaching out to the MSDN community to see if anyone has experienced this issue with
Web Site Projects.
I hope that clears up the Project Type question.
Moojjoo MCP, MCTS
MCP Virtual Business Card
http://moojjoo.blogspot.com

Getting error message Cannot Resolve Symbol when trying to compile a class

Hello All -
I am getting an error message cannot resolve symbol while trying to compile a java class that calls another java class in the same package. The called class compiles fine, but the calling class generates
the following error message:
D:\Apache Tomcat 4.0\webapps\examples\WEB-INF\classes\cal>javac
ConnectionPool.java
ConnectionPool.java:158: cannot resolve symbol
symbol : class PooledConnection
location: class cal.ConnectionPool
private void addConnection(PooledConnection value) {
^
ConnectionPool.java:144: cannot resolve symbol
symbol : class PooledConnection
location: class cal.ConnectionPool
PooledConnection pcon = new PooledConnection(con);
^
ConnectionPool.java:144: cannot resolve symbol
symbol : class PooledConnection
location: class cal.ConnectionPool
PooledConnection pcon = new PooledConnection(con);
The code is listed as follows for PooledConnection.java (it compiles fine)
package cal;
import java.sql.*;
public class PooledConnection {
// Real JDBC Connection
private Connection connection = null;
// boolean flag used to determine if connection is in use
private boolean inuse = false;
// Constructor that takes the passed in JDBC Connection
// and stores it in the connection attribute.
public PooledConnection(Connection value) {
if ( value != null ) {
connection = value;
// Returns a reference to the JDBC Connection
public Connection getConnection() {
// get the JDBC Connection
return connection;
// Set the status of the PooledConnection.
public void setInUse(boolean value) {
inuse = value;
// Returns the current status of the PooledConnection.
public boolean inUse() {
return inuse;
// Close the real JDBC Connection
public void close() {
try {
connection.close();
catch (SQLException sqle) {
System.err.println(sqle.getMessage());
Now the code for ConnectionPool.java class that gives the cannot
resolve symbol error
package cal;
import java.sql.*;
import java.util.*;
public class ConnectionPool {
// JDBC Driver Name
private String driver = null;
// URL of database
private String url = null;
// Initial number of connections.
private int size = 0;
// Username
private String username = new String("");
// Password
private String password = new String("");
// Vector of JDBC Connections
private Vector pool = null;
public ConnectionPool() {
// Set the value of the JDBC Driver
public void setDriver(String value) {
if ( value != null ) {
driver = value;
// Get the value of the JDBC Driver
public String getDriver() {
return driver;
// Set the URL Pointing to the Datasource
public void setURL(String value ) {
if ( value != null ) {
url = value;
// Get the URL Pointing to the Datasource
public String getURL() {
return url;
// Set the initial number of connections
public void setSize(int value) {
if ( value > 1 ) {
size = value;
// Get the initial number of connections
public int getSize() {
return size;
// Set the username
public void setUsername(String value) {
if ( value != null ) {
username = value;
// Get the username
public String getUserName() {
return username;
// Set the password
public void setPassword(String value) {
if ( value != null ) {
password = value;
// Get the password
public String getPassword() {
return password;
// Creates and returns a connection
private Connection createConnection() throws Exception {
Connection con = null;
// Create a Connection
con = DriverManager.getConnection(url,
username, password);
return con;
// Initialize the pool
public synchronized void initializePool() throws Exception {
// Check our initial values
if ( driver == null ) {
throw new Exception("No Driver Name Specified!");
if ( url == null ) {
throw new Exception("No URL Specified!");
if ( size < 1 ) {
throw new Exception("Pool size is less than 1!");
// Create the Connections
try {
// Load the Driver class file
Class.forName(driver);
// Create Connections based on the size member
for ( int x = 0; x < size; x++ ) {
Connection con = createConnection();
if ( con != null ) {
// Create a PooledConnection to encapsulate the
// real JDBC Connection
PooledConnection pcon = new PooledConnection(con);
// Add the Connection to the pool.
addConnection(pcon);
catch (Exception e) {
System.err.println(e.getMessage());
throw new Exception(e.getMessage());
// Adds the PooledConnection to the pool
private void addConnection(PooledConnection value) {
// If the pool is null, create a new vector
// with the initial size of "size"
if ( pool == null ) {
pool = new Vector(size);
// Add the PooledConnection Object to the vector
pool.addElement(value);
public synchronized void releaseConnection(Connection con) {
// find the PooledConnection Object
for ( int x = 0; x < pool.size(); x++ ) {
PooledConnection pcon =
(PooledConnection)pool.elementAt(x);
// Check for correct Connection
if ( pcon.getConnection() == con ) {
System.err.println("Releasing Connection " + x);
// Set its inuse attribute to false, which
// releases it for use
pcon.setInUse(false);
break;
// Find an available connection
public synchronized Connection getConnection()
throws Exception {
PooledConnection pcon = null;
// find a connection not in use
for ( int x = 0; x < pool.size(); x++ ) {
pcon = (PooledConnection)pool.elementAt(x);
// Check to see if the Connection is in use
if ( pcon.inUse() == false ) {
// Mark it as in use
pcon.setInUse(true);
// return the JDBC Connection stored in the
// PooledConnection object
return pcon.getConnection();
// Could not find a free connection,
// create and add a new one
try {
// Create a new JDBC Connection
Connection con = createConnection();
// Create a new PooledConnection, passing it the JDBC
// Connection
pcon = new PooledConnection(con);
// Mark the connection as in use
pcon.setInUse(true);
// Add the new PooledConnection object to the pool
pool.addElement(pcon);
catch (Exception e) {
System.err.println(e.getMessage());
throw new Exception(e.getMessage());
// return the new Connection
return pcon.getConnection();
// When shutting down the pool, you need to first empty it.
public synchronized void emptyPool() {
// Iterate over the entire pool closing the
// JDBC Connections.
for ( int x = 0; x < pool.size(); x++ ) {
System.err.println("Closing JDBC Connection " + x);
PooledConnection pcon =
(PooledConnection)pool.elementAt(x);
// If the PooledConnection is not in use, close it
if ( pcon.inUse() == false ) {
pcon.close();
else {
// If it is still in use, sleep for 30 seconds and
// force close.
try {
java.lang.Thread.sleep(30000);
pcon.close();
catch (InterruptedException ie) {
System.err.println(ie.getMessage());
I am using Sun JDK Version 1.3.0_02" and Apache/Tomcat 4.0. Both the calling and the called class are in the same directory.
Any help would be greatly appreciated.
tnx..
addi

Is ConnectionPool in this "cal" package as well as PooledConnection? From the directory you are compiling from it appears that it is. If it is, then you are compiling it incorrectly. To compile ConnectionPool (and PooledConnection similarly), you must change the current directory to the one that contains cal and type
javac cal/ConnectionPool.

Class error - cannot resolve symbol "MyDocumentListener"

Hello,
this is a groaner I'm sure, but I don't see the problem.
Newbie-itis probably ...
I'm not concerned with what the class does, but it would be nice for the silly thing to compile!
What the heck am I missing for "MyDocumentListener" ?
C:\divelog>javac -classpath C:\ CenterPanel.java
CenterPanel.java:53: cannot resolve symbol
symbol : class MyDocumentListener
location: class divelog.CenterPanel
MyDocumentListener myDocumentListener = new MyDocumentListener(); // define the listener class
^
CenterPanel.java:53: cannot resolve symbol
symbol : class MyDocumentListener
location: class divelog.CenterPanel
MyDocumentListener myDocumentListener = new MyDocumentListener(); // define the listener class
^
2 errors
package divelog;
import java.awt.*;
import java.awt.event.*;
import java.io.*;
import java.lang.*;
import javax.swing.*;
import javax.swing.event.*;
import javax.swing.filechooser.*;
import javax.swing.text.*;
public class CenterPanel extends JPanel implements ActionListener
{ // Opens class
static private final String newline = "\n";
private JTextArea comments;
private JScrollPane scrollpane;
private JButton saveButton, openButton;
private JLabel whiteshark;
private Box box;
private BufferedReader br ;
private String str;
private JTextArea instruct;
private File defaultDirectory = new File("C://divelog");
private File fileDirectory = null;
private File currentFile= null;
public CenterPanel()
{ // open constructor CenterPanel
setBackground(Color.white);
comments = new JTextArea("Enter comments, such as " +
"location, water conditions, sea life you observed," +
" and problems you may have encountered.", 15, 10);
comments.setLineWrap(true);
comments.setWrapStyleWord(true);
comments.setEditable(true);
comments.setFont(new Font("Times-Roman", Font.PLAIN, 14));
// add a document listener for changes to the text,
// query before opening a new file to decide if we need to save changes.
MyDocumentListener myDocumentListener = new MyDocumentListener(); // define the listener class
comments.getDocument().addDocumentListener(myDocumentListener); // create the reference for the class
// ------ Document listener class -----------
class MyDocumentListener implements DocumentListener {
public void insertUpdate(DocumentEvent e) {
Calculate(e);
public void removeUpdate(DocumentEvent e) {
Calculate(e);
public void changedUpdate(DocumentEvent e) {
private void Calculate(DocumentEvent e) {
// do something here
scrollpane = new JScrollPane(comments);
scrollpane.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_ALWAYS);
saveButton = new JButton("Save Comments", new ImageIcon("images/Save16.gif"));
saveButton.addActionListener( this );
saveButton.setToolTipText("Click this button to save the current file.");
openButton = new JButton("Open File...", new ImageIcon("images/Open16.gif"));
openButton.addActionListener( this );
openButton.setToolTipText("Click this button to open a file.");
whiteshark = new JLabel("", new ImageIcon("images/gwhite.gif"), JLabel.CENTER);
Box boxH;
boxH = Box.createHorizontalBox();
boxH.add(openButton);
boxH.add(Box.createHorizontalStrut(15));
boxH.add(saveButton);
box = Box.createVerticalBox();
box.add(scrollpane);
box.add(Box.createVerticalStrut(10));
box.add(boxH);
box.add(Box.createVerticalStrut(15));
box.add(whiteshark);
add(box);
} // closes constructor CenterPanel
public void actionPerformed( ActionEvent evt )
{ // open method actionPerformed
JFileChooser jfc = new JFileChooser();
// these do not work !!
// -- set the file types to view --
// ExtensionFileFilter filter = new ExtensionFileFilter();
// FileFilter filter = new FileFilter();
//filter.addExtension("java");
//filter.addExtension("txt");
//filter.setDescription("Text & Java Files");
//jfc.setFileFilter(filter);
     //Add a custom file filter and disable the default "Accept All" file filter.
jfc.addChoosableFileFilter(new JTFilter());
jfc.setAcceptAllFileFilterUsed(false);
// -- open the default directory --
// public void setCurrentDirectory(File dir)
// jfc.setCurrentDirectory(new File("C://divelog"));
jfc.setCurrentDirectory(defaultDirectory);
jfc.setSize(400, 300);
jfc.setFileSelectionMode(JFileChooser.FILES_AND_DIRECTORIES);
Container parent = saveButton.getParent();
//========================= Test Button Actions ================================
//========================= Open Button ================================
if (evt.getSource() == openButton)
int choice = jfc.showOpenDialog(CenterPanel.this);
File file = jfc.getSelectedFile();
/* a: */
if (file != null && choice == JFileChooser.APPROVE_OPTION)
String filename = jfc.getSelectedFile().getAbsolutePath();
// -- compare the currentFile to the file chosen, alert of loosing any changes to currentFile --
// If (currentFile != filename)
// -- get the current directory name -------
// public File getCurrentDirectory( );
File f=new File(System.getProperty("user.dir"));
fileDirectory = jfc.getCurrentDirectory();
// -- remember the last directory used --
if (defaultDirectory != fileDirectory)
{defaultDirectory = fileDirectory;}
try
{ //opens try
comments.getLineCount( );
// -- clear the old data before importing the new file --
comments.selectAll();
comments.replaceSelection("");
// -- get the new data ---
br = new BufferedReader (new FileReader(file));
while ((str = br.readLine()) != null)
{//opens while
comments.append(str);
} //closes while
} // close try
catch (IOException ioe)
{ // open catch
comments.append(newline +"Open command not successful:" + ioe + newline);
} // close catch
// ---- display the values of the directory variables -----------------------
comments.append(
newline + "The f directory variable contains: " + f +
newline + "The fileDirectory variable contains: " + fileDirectory +
newline + "The defaultDirectory variable contains: " + defaultDirectory );
else
comments.append("Open command cancelled by user." + newline);
} //close if statement /* a: */
//========================= Save Button ================================
} else if (evt.getSource() == saveButton)
int choice = jfc.showSaveDialog(CenterPanel.this);
if (choice == JFileChooser.APPROVE_OPTION)
File fileName = jfc.getSelectedFile();
// -- get the current directory name -------
// public File getCurrentDirectory( );
File f=new File(System.getProperty("user.dir"));
fileDirectory = jfc.getCurrentDirectory();
// -- remember the last directory used --
if (defaultDirectory != fileDirectory)
{defaultDirectory = fileDirectory;}
//check for existing files. Warn users & ask if they want to overwrite
for(int i = 0; i < fileName.length(); i ++) {
File tmp = null;
tmp = (fileName);
if (tmp.exists()) // display pop-up alert
//public static int showConfirmDialog( Component parentComponent,
// Object message,
// String title,
// int optionType,
// int messageType,
// Icon icon);
int confirm = JOptionPane.showConfirmDialog(null,
fileName + " already exists on " + fileDirectory
+ "\n \nContinue?", // msg
"Warning! Overwrite File!", // title
JOptionPane.OK_CANCEL_OPTION, // buttons displayed
                    // JOptionPane.ERROR_MESSAGE
                    // JOptionPane.INFORMATION_MESSAGE
                    // JOptionPane.PLAIN_MESSAGE
                    // JOptionPane.QUESTION_MESSAGE
JOptionPane.WARNING_MESSAGE,
null);
if (confirm != JOptionPane.YES_OPTION)
{ //user cancels the file overwrite.
try {
jfc.cancelSelection();
break;
catch(Exception e) {}
// ----- Save the file if everything is OK ----------------------------
try
{ // opens try
BufferedWriter bw = new BufferedWriter(new FileWriter(fileName));
bw.write(comments.getText());
bw.flush();
bw.close();
comments.append( newline + newline + "Saving: " + fileName.getName() + "." + newline);
break;
} // closes try
catch (IOException ioe)
{ // open catch
comments.append(newline +"Save command unsuccessful:" + ioe + newline);
} // close catch
} // if exists
} //close for loop
else
comments.append("Save command cancelled by user." + newline);
} // end-if save button
} // close method actionPerformed
} //close constructor CenterPanel
} // Closes class CenterPanel

There is no way to be able to see MyDocumentListener class in the way you wrote. The reason is because MyDocumentListener class inside the constructor itself. MyDocumentListener class is an inner class, not suppose to be inside a constructor or a method. What you need to do is simple thing, just move it from inside the constructor and place it between two methods.
that's all folks
Qusay

PLEASE HELP: cannot resolve symbol class

it's showing me the error on the following lines 7 and 9
it says cannot resolve symbol class Name and cannot resolve symbol class Phone
I also have a package name addressBook and it contains two files Entry.java and Address.java
Here is the code:
import java.io.*;
import addressBook.*;
public class AddressDr
     public static void main(String[] args)throws IOException
          Name name;
          Address address;
          Phone phone;
          Entry entry;
          String first, last, middle, street, city, state, zip;
          int areaCode, number;
          BufferedReader in;
          in=new BufferedReader(new InputStreamReader(System.in));
          PrintWriter outFile;
          outFile=new PrintWriter(new FileWriter("Entries"));
          System.out.println("Quit entered fot the first name ends the " + "application.");
          System.out.print("Enter first name: ");
          first=in.readLine();
          while (first.compareTo("Quit") !=0)
               System.out.print("Enter last name: ");
               last=in.readLine();
               System.out.print("Enter middle name: ");
               middle=in.readLine();
               name=new Name(first, last, middle);
               System.out.print("Enter street address: ");
               street=in.readLine();
               System.out.print("Enter city: ");
               city=in.readLine();
               System.out.print("Enter state: ");
               state=in.readLine();
               System.out.print("Enter ZIP code: ");
               zip=in.readLine();
               address=new Address(street, city, state, zip);
               System.out.print("Enter areaCode: ");
               areaCode = Integer.parseInt(in.readLine());
               System.out.print("Enter number: ");
               number=Integer.parseInt(in.readLine());
               phone=new Phone(areaCode, number);
               entry= new Entry(name, address, phone);
               entry.writeToFile(outFile);
               System.out.print("Enter first name: ");
               first=in.readLine();
          outFile.close();
}

OK. Here is how I did it.
I have AddressDr which is Address driver.
I have two files Address and Entry which in package addressBook.
AddressDr:
import java.io.*;
import addressBook.*;
public class AddressDr
     public static void main(String[] args)throws IOException
          Name name;
          Address address;
          Phone phone;
          Entry entry;
          String first, last, middle, street, city, state, zip;
          int areaCode, number;
          BufferedReader in;
          in=new BufferedReader(new InputStreamReader(System.in));
          PrintWriter outFile;
          outFile=new PrintWriter(new FileWriter("Entries"));
          System.out.println("Quit entered fot the first name ends the " + "application.");
          System.out.print("Enter first name: ");
          first=in.readLine();
          while (first.compareTo("Quit") !=0)
               System.out.print("Enter last name: ");
               last=in.readLine();
               System.out.print("Enter middle name: ");
               middle=in.readLine();
               name=new Name(first, last, middle);
               System.out.print("Enter street address: ");
               street=in.readLine();
               System.out.print("Enter city: ");
               city=in.readLine();
               System.out.print("Enter state: ");
               state=in.readLine();
               System.out.print("Enter ZIP code: ");
               zip=in.readLine();
               address=new Address(street, city, state, zip);
               System.out.print("Enter areaCode: ");
               areaCode = Integer.parseInt(in.readLine());
               System.out.print("Enter number: ");
               number=Integer.parseInt(in.readLine());
               phone=new Phone(areaCode, number);
               entry= new Entry(name, address, phone);
               entry.writeToFile(outFile);
               System.out.print("Enter first name: ");
               first=in.readLine();
          outFile.close();
Entry:
package addressBook;
import java.io.*;
public class Entry
     Name name;
     Address address;
     Phone phone;
public Entry(Name newName, Address newAddress, Phone phoneNumber)
     name = newName;
     address = newAddress;
     phone = phoneNumber;
public Name knowName()
     return name;
public Address knowAddress()
     return address;
public Phone knowPhone()
     return phone;
public void writeToFile(PrintWriter outFile)
     outFile.println(name.knowFirstName());
     outFile.println(name.knowLastName());
     outFile.println(name.knowMiddleName());
     oufFile.println(address.knowStreet());
     outFile.println(address.knowState());
     outFile.println(address.knowCity());
     outFile.println(address.knowZip());
     outFile.println(phone.knowAreaCode());
     outFile.println(phone.knowDigits());
Address:
package addressBook;
public class Address
     String street;
     String city;
     String state;
     String zipCode;
     public Address(String newStreet, String newCity, String newState, String zip)
          street=newStreet;
          city=newCity;
          state=newState;
          zipCode=zip;
     public String knowStreet()
          return street;
     public String knowCity()
          return city;
     public String knowState()
          return state;
     public String knowZip()
          return zipCode;
}

Recieving cannot resolve symbol symbol : class Serializable

I'm receiving the error:
cannot resolve symbol symbol : class Serializable
The class is as follows:
//package cscie160.hw5;
import java.io.Serializable
* @author Eddie Brodie
* @version %I%, %G%
public class AccountInfo implements Serializable
     public int _accountNumber;
     public int _pin;
     public AccountInfo(int accountNumber, int pin)
          _accountNumber = accountNumber;
          _pin = pin;
I've tried importing java.*
I've also checked my classpath.
Any ideas?

Try taking the import statement out of the comment block; that might help

Cannot resolve symbol: class OracleDriver

Attempting to compile a servlet on Apache Server using same jdeveloper jdbc libraries:
classes12.jar & nls_charset12.jar
Error message:
$compilejava2.sh ProdJobs
ProdJobs.java:361: cannot resolve symbol
symbol : class OracleDriver
location: package driver
DriverManager.registerDriver(new oracle.jdbc.driver.OracleDriver());
Am I missing something else?
Jeffrey

Enter this code into your program and then put the Oracle jar file that contains the driver in your run-time classpath.
try {
Class.forName("oracle.jdbc.driver.OracleDriver");
catch(ClassNotFoundException cnfe) {
// driver not found
}The effect of this is that the classloader will load the Oracle driver for you then call it's static initiailizer that does a bunch of magic that results in the Java runtime knowing that there's a JDBC driver out there.
It is a little weird - but that's the way it works.

Cannot resolve symbol: class EJBObject

Using javac I get this compile error on this file Calculator.java
Calculator.java:1: cannot resolve symbol
symbol : class EJBObject
location: package ejb
import javax.ejb.EJBObject;
^
Calculator.java:5: cannot resolve symbol
symbol : class EJBObject
location: interface Calculator
public interface Calculator extends EJBObject {
Source code for Calculator.java
import javax.ejb.EJBObject;
import java.rmi.*;
public interface Calculator extends EJBObject {
public long add (int x, int y) throws RemoteException;
public long subtract (int x, int y) throws RemoteException;

This code is from a book, so I will assume its a classpath problem. My
classpath looks like:
"C\QTJava.zip".;%J2EE_HOME%\lib\j2ee.jar;%J2EE_HOME%\lib\locale
Also the following enviorment varibales have been set to:
J2EE_HOME
C:\Development\Java\j2sdkee1.3.1
JAVA_HOME
C:\Development\Java\jdk1.3.1
Path
%SystemRoot%\system32;%SystemRoot%;%SystemRoot%\System32\Wbem;C:\Program Files\Common Files\Adaptec Shared\System;%JAVA_HOME%\bin;%J2EE_HOME%\bin
I can run j2EE, like "j2EE -verbose" (no problems)
also run cloudscape, like "cloudscape -start" (no problems)
also can run deploytool, like "deploytool" (no problems, & deploy sample ear files from cd book)
Your help is appreicated.

Cannot resolve symbol class graphics

does anyone know what the error
cannot resolve symbol class graphics means?
with this code i can't seem to call the graphics method to draw the line....any reason why?
import javax.swing.*;
import java.*;
public class LineDraw extends JFrame {
    public static void main(String[] args) {
        LineDraw ld = new LineDraw();
        ld.setSize(500,500);
        ld.setVisible(true);
        ld.enterVariables();
    public void init(){
    private int x1;
    private int x2;
    private int y1;
    private int y2;
    public void paint(Graphics g) {
        g.GetGraphics(g);
        super.paintComponent(g);
        g.drawLine(x1, y1, x2, y2);
    public void enterVariables() {
        x1 = Integer.parseInt(JOptionPane.showInputDialog("Enter x1:"));
        y1 = Integer.parseInt(JOptionPane.showInputDialog("Enter y1:"));
        x2 = Integer.parseInt(JOptionPane.showInputDialog("Enter x2:"));
        y2 = Integer.parseInt(JOptionPane.showInputDialog("Enter y2:"));
        repaint();
}

well the exact error message is ...by the way now that i think about it
if the graphics method shoudl not be part of the JFrame class then what method would i use to draw 2D Graphics?
--------------------Configuration: <Default>--------------------
C:\Documents and Settings\c1s5\My Documents\LineDraw.java:21: cannot resolve symbol
symbol : class Graphics
location: class LineDraw
public void paint(Graphics g)
^
1 error
Process completed.
and the exact code is
import javax.swing.*;
import java.*;
public class LineDraw extends JFrame {
    public static void main(String[] args) {
        LineDraw ld = new LineDraw();
        ld.setSize(1024,500);
        ld.setVisible(true);
        ld.enterVariables();
    private int x1;
    private int x2;
    private int y1;
    private int y2;
    public void paint(Graphics g)
        super.paintComponent(g);
        g.drawLine(x1, y1, x2, y2);
    public void enterVariables() {
        x1 = Integer.parseInt(JOptionPane.showInputDialog("Enter x1:"));
        y1 = Integer.parseInt(JOptionPane.showInputDialog("Enter y1:"));
        x2 = Integer.parseInt(JOptionPane.showInputDialog("Enter x2:"));
        y2 = Integer.parseInt(JOptionPane.showInputDialog("Enter y2:"));
        repaint();
}

Cannot resolve symbol error even with class imported

Hi
I'm trying to print out a java.version system property but keep getting a
cannot resolve symbol error
symbol: class getProperty
location: class java.lang.System
I've looked at the API and getProperty() is a method of lang.System
Can anyone throw any light?
thanks
import java.lang.System;
class PropertiesTest {
    public static void main(String[] args) {
            String v = new System.getProperty("java.version");
             System.out.println(v);
}

Thanks Jos
It compiles but I now get a runtime error
Exception in thread "main"
java.lang.NoClassDefFoundError:PropertiesTest
What do you reckon is the problem?
thanks
java -cp .;<any other directories or jars>
YourClassNameYou get a NoClassDefFoundError message because the
JVM (Java Virtual Machine) can't find your class. The
way to remedy this is to ensure that your class is
included in the classpath. The example assumes that
you are in the same directory as the class you're
trying to run.I know it's a bad habit but I've put this file (PropertiesTest.java) and the compiled class (PropertiesTest.class) both in my bin folder which contains the javac compiler

Cannot resolve symbol : class odbc ERROR

Hi Helper
I am trying to compile a the following and I am getting the error
C:\jdk\websiter>javac MainServlet.java
MainServlet.java:86: cannot resolve symbol
symbol : class odbc
location: package jdbc
Class.forName(sun.jdbc.odbc.JdbcOdbcDriver);
import javax.servlet.*;
import javax.servlet.http.*;
import java.sql.*;
import java.io.*;
import java.util.*;
* This is the servlet to send the user the names of all the sites present in the database
public class MainServlet extends HttpServlet implements ServletConstants
Connection m_con;
PreparedStatement m_pstmt;
ResultSet m_res;
Vector m_vecsiteName;
public void Init(ServletConfig config) throws ServletException {
     super.init(config);
}// end of init()
public void service(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
          m_vecsiteName = new Vector();
     try {
     Class.forName(sun.jdbc.odbc.JdbcOdbcDriver);
m_con = DriverManager.getConnection("jdbc:odbc:sitewd", "", "");
How can i fix it? thanks
VT

Replace the Statement
Class.forName(sun.jdbc.odbc.JdbcOdbcDriver);
as
Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");

Cannot resolve symbol class Scanner (Error)

For whatever reason I get the error message "cannot resolve symbol class Scanner" when trying to run this:
import java.io.*;
import java.util.*;
public class NameReversal
     public static void main(String args[])
          System.out.print("Enter your name: ");
          Scanner Reader = new Scanner(System.in);
          String first = Reader.next();
          String finl = Reader.next();
          int z = first.length();
          int v = finl.length();
          int y = z-1;
          int f = y-1;
          for(int i = y; i>=0; z--)
          System.out.print(first.charAt(1));
          System.out.print(" ");
          for(int p = f; p >= 0; p--)
          System.out.println(finl.charAt(p));
}

The Scanner class is in the JDK version 1.5 or later. You must be using an earlier version.

Error:cannot resolve Symbol class"name"

when I have compiled Bean class named SlBean which has primary class named pk, I recevied following error message(I compiled pk class without error) :
cannot resolve symbol
symbol : class pk
location: class SlBean
public pk ejbCreate(

Sorry , its not classpath problem. You have to simply import the pk class if its in any package. I am assuming you have packaged your pk class with ejb jar file.
for eg. if your class is
package abc.xyz
public class pk
then in your bean class import
import abc.xyz.pk;
--Ashwani

Cannot resolve symbol when the classes are in the same package

i have one interface and two classes all in the same package. am getting " cannot resolve symbol", when the code refers to the interface or the class .
the package name is collections.impl and
the directory i used to store all the java files:
c:\jdk\bin\collections\impl.
isthere any othe option other than compiling all the files from the comand line at the same time?
please help - i m new to java.

If you have:
I.java:
package some;
public interface I {
    void method();
}A.java:
package some;
public class A implements I {
    public void method() {
        new B();
}B.java:
package some;
public class B implements I {
    public void method() {
        new A();
}in c:/temp/some for example
you can compile your files with
javac c:/temp/some/*.java
It seems that you have errors in your code.
Recheck it twice or use NetBeans IDE(http://www.netbeans.org) it will do this for you ;)

Cannot resolve symbol error when compiling a class that calls another class

I've read all the other messages that include "cannot resolve symbol", but no luck. I've got a small app - 3 classes all in the same package. BlackjackDAO and Player compile OK, but BlackjackServlet throws the "cannot resolve symbol" (please see pertinent code below)...
I've tried lots: ant and javac compiling, upgrading my version of tomcat, upgrading my version of jdk/jre, making sure my servlet.jar is being seen by the compiler (at least as far as I can see from the -verbose feedback)...any help would be GREAT! Thanks in advance...
classes: BlackjackServlet, BlackjackDAO, Player
package: myblackjackpackage
tomcat version: 4.1.1.8
jdk version: j2sdk 1.4.0
ant version: 1.4.1
I get the same error message from Ant and Javac...
C:\Tomcat4118\src\webapps\helloblackjack\src\myblackjackpackage>javac *.java -verbose
C:\Tomcat4118\src\webapps\helloblackjack>ant all -verbose
compile error:
BlackjackServlet.java:55: cannot resolve symbol
symbol: method addPlayer (javax.servlet.http.HttpServletRequest,javax.servlet.http.Http
ServletResponse)
location: class myblackjackpackage.BlackjackServlet
          addPlayer(request, response);
^
My code is:
package myblackjackpackage;
import java.io.*;
import java.util.*;
import javax.servlet.*;
import javax.servlet.http.*;
import java.sql.*;
import java.lang.*;
/** controller servlet in a web based blackjack game application @author Ethan Harlow */
public class BlackjackServlet extends HttpServlet {
     private BlackjackDAO theBlackjackDAO;
     public void init() throws ServletException {
String driver = "com.microsoft.jdbc.sqlserver.SQLServerDriver";
String dbUrl = "jdbc:microsoft:sqlserver://localhost:1433";
String userid = "testlogin";
String passwrd = "testpass";
     try {
     theBlackjackDAO = new BlackjackDAO(driver, dbUrl, userid, passwrd);
     catch (IOException exc) {
          System.err.println(exc.toString());
     catch (ClassNotFoundException cnf) {
          System.err.println(cnf.toString());
     catch (SQLException seq) {
          System.err.println(seq.toString());
public void doPost(HttpServletRequest request, HttpServletResponse response)
          throws ServletException, IOException {
doGet(request, response);
public void doGet(HttpServletRequest request, HttpServletResponse response)
          throws ServletException, IOException {
     String command = request.getParameter("command");
     if (command == null || (command.equals("stats"))) {
     else if (command.equals("add")) {
          try {
//the following line is caught by compiler
          addPlayer(request, response);
          response.setContentType("text/html");
          PrintWriter out = response.getWriter();
          out.println("<html>");
          out.println("<body>");
          out.println("<p>Hi, your command was " + request.getParameter("command") + "!!!</p>");
          out.println("</body>");
          out.println("</html>");
          catch (Exception exc) {
               System.err.println(exc.toString());
     else if (command.equals("play")) {
     else if (command.equals("bet")) {
     else if (command.equals("hit")) {
     else if (command.equals("stand")) {
     else if (command.equals("split")) {
     else if (command.equals("double")) {
     else if (command.equals("dealerdecision")) {
     else if (command.equals("reinvest")) {
     else if (command.equals("changebet")) {
     else if (command.equals("deal")) {
package myblackjackpackage;
import java.io.*;
import java.util.*;
import javax.servlet.*;
import javax.servlet.http.*;
import java.sql.*;
import java.lang.*;
public class BlackjackDAO {
     private Connection myConn;
     public BlackjackDAO(String driver, String dbUrl, String userid, String passwrd)
               throws IOException, ClassNotFoundException, SQLException {
          System.out.println("Loading driver: " + driver);
          Class.forName(driver);
          System.out.println("Connection to: " + dbUrl);
          myConn = DriverManager.getConnection(dbUrl, userid, passwrd);
          System.out.println("Connection successful!");
     public void addPlayer(HttpServletRequest request, HttpServletResponse response)
               throws IOException, SQLException {
//I've commented out all my code while debugging, so I didn't include
//any here
compiler feedback
C:\Tomcat4118\src\webapps\helloblackjack\src\myblackjackpackage>javac *.java -verbose
[parsing started BlackjackDAO.java]
[parsing completed 90ms]
[parsing started BlackjackServlet.java]
[parsing completed 10ms]
[parsing started Player.java]
[parsing completed 10ms]
[loading c:\j2sdk14003\jre\lib\rt.jar(java/lang/Object.class)]
[loading c:\j2sdk14003\jre\lib\rt.jar(java/sql/Connection.class)]
[loading c:\j2sdk14003\jre\lib\rt.jar(java/lang/String.class)]
[loading c:\j2sdk14003\jre\lib\rt.jar(java/io/IOException.class)]
[loading c:\j2sdk14003\jre\lib\rt.jar(java/lang/ClassNotFoundException.class)]
[loading c:\j2sdk14003\jre\lib\rt.jar(java/sql/SQLException.class)]
[loading c:\tomcat4118\common\lib\servlet.jar(javax/servlet/http/HttpServletRequ
est.class)]
[loading c:\tomcat4118\common\lib\servlet.jar(javax/servlet/http/HttpServletResp
onse.class)]
[loading c:\tomcat4118\common\lib\servlet.jar(javax/servlet/http/HttpServlet.cla
ss)]
[loading c:\tomcat4118\common\lib\servlet.jar(javax/servlet/GenericServlet.class
[loading c:\tomcat4118\common\lib\servlet.jar(javax/servlet/Servlet.class)]
[loading c:\tomcat4118\common\lib\servlet.jar(javax/servlet/ServletConfig.class)
[loading c:\j2sdk14003\jre\lib\rt.jar(java/io/Serializable.class)]
[loading c:\tomcat4118\common\lib\servlet.jar(javax/servlet/ServletException.cla
ss)]
[checking myblackjackpackage.BlackjackDAO]
[loading c:\j2sdk14003\jre\lib\rt.jar(java/lang/Throwable.class)]
[loading c:\j2sdk14003\jre\lib\rt.jar(java/lang/Exception.class)]
[loading c:\j2sdk14003\jre\lib\rt.jar(java/lang/System.class)]
[loading c:\j2sdk14003\jre\lib\rt.jar(java/io/PrintStream.class)]
[loading c:\j2sdk14003\jre\lib\rt.jar(java/io/FilterOutputStream.class)]
[loading c:\j2sdk14003\jre\lib\rt.jar(java/io/OutputStream.class)]
[loading c:\j2sdk14003\jre\lib\rt.jar(java/lang/Class.class)]
[loading c:\j2sdk14003\jre\lib\rt.jar(java/sql/DriverManager.class)]
[loading c:\j2sdk14003\jre\lib\rt.jar(java/util/Properties.class)]
[loading c:\j2sdk14003\jre\lib\rt.jar(java/lang/Error.class)]
[loading c:\j2sdk14003\jre\lib\rt.jar(java/lang/RuntimeException.class)]
[loading c:\j2sdk14003\jre\lib\rt.jar(java/lang/StringBuffer.class)]
[wrote BlackjackDAO.class]
[checking myblackjackpackage.BlackjackServlet]
[loading c:\tomcat4118\common\lib\servlet.jar(javax/servlet/ServletRequest.class
BlackjackServlet.java:55: cannot resolve symbol
symbol : method addPlayer (javax.servlet.http.HttpServletRequest,javax.servlet
.http.HttpServletResponse)
location: class myblackjackpackage.BlackjackServlet
addPlayer(request, response);
^
[loading c:\tomcat4118\common\lib\servlet.jar(javax/servlet/ServletResponse.clas
s)]
[loading c:\j2sdk14003\jre\lib\rt.jar(java/io/PrintWriter.class)]
[loading c:\j2sdk14003\jre\lib\rt.jar(java/io/Writer.class)]
[checking myblackjackpackage.Player]
[total 580ms]
1 error
C:\Tomcat4118\src\webapps\helloblackjack\src\myblackjackpackage>
and here's the ant feedback...
C:\Tomcat4118\src\webapps\helloblackjack>ant all -verbose
Ant version 1.4.1 compiled on October 11 2001
Buildfile: build.xml
Detected Java version: 1.4 in: c:\j2sdk14003\jre
Detected OS: Windows 2000
parsing buildfile C:\Tomcat4118\src\webapps\helloblackjack\build.xml with URI =
file:C:/Tomcat4118/src/webapps/helloblackjack/build.xml
Project base dir set to: C:\Tomcat4118\src\webapps\helloblackjack
Build sequence for target `all' is [clean, prepare, compile, all]
Complete build sequence is [clean, prepare, compile, all, javadoc, deploy, dist]
clean:
[delete] Deleting directory C:\Tomcat4118\src\webapps\helloblackjack\build
[delete] Deleting C:\Tomcat4118\src\webapps\helloblackjack\build\images\a_s.g
if
[delete] Deleting C:\Tomcat4118\src\webapps\helloblackjack\build\images\q_s.g
if
[delete] Deleting directory C:\Tomcat4118\src\webapps\helloblackjack\build\im
ages
[delete] Deleting C:\Tomcat4118\src\webapps\helloblackjack\build\index.html
[delete] Deleting C:\Tomcat4118\src\webapps\helloblackjack\build\newplayer.ht
ml
[delete] Deleting C:\Tomcat4118\src\webapps\helloblackjack\build\WEB-INF\clas
ses\myblackjackpackage\BlackjackDAO.class
[delete] Deleting directory C:\Tomcat4118\src\webapps\helloblackjack\build\WE
B-INF\classes\myblackjackpackage
[delete] Deleting directory C:\Tomcat4118\src\webapps\helloblackjack\build\WE
B-INF\classes
[delete] Deleting C:\Tomcat4118\src\webapps\helloblackjack\build\WEB-INF\web.
xml
[delete] Deleting directory C:\Tomcat4118\src\webapps\helloblackjack\build\WE
B-INF
[delete] Deleting directory C:\Tomcat4118\src\webapps\helloblackjack\build
prepare:
[mkdir] Created dir: C:\Tomcat4118\src\webapps\helloblackjack\build
[copy] images\a_s.gif added as C:\Tomcat4118\src\webapps\helloblackjack\bui
ld\images\a_s.gif doesn't exist.
[copy] images\q_s.gif added as C:\Tomcat4118\src\webapps\helloblackjack\bui
ld\images\q_s.gif doesn't exist.
[copy] index.html added as C:\Tomcat4118\src\webapps\helloblackjack\build\i
ndex.html doesn't exist.
[copy] newplayer.html added as C:\Tomcat4118\src\webapps\helloblackjack\bui
ld\newplayer.html doesn't exist.
[copy] WEB-INF\web.xml added as C:\Tomcat4118\src\webapps\helloblackjack\bu
ild\WEB-INF\web.xml doesn't exist.
[copy] omitted as C:\Tomcat4118\src\webapps\helloblackjack\build is up to
date.
[copy] images added as C:\Tomcat4118\src\webapps\helloblackjack\build\image
s doesn't exist.
[copy] WEB-INF added as C:\Tomcat4118\src\webapps\helloblackjack\build\WEB-
INF doesn't exist.
[copy] Copying 5 files to C:\Tomcat4118\src\webapps\helloblackjack\build
[copy] Copying C:\Tomcat4118\src\webapps\helloblackjack\web\images\q_s.gif
to C:\Tomcat4118\src\webapps\helloblackjack\build\images\q_s.gif
[copy] Copying C:\Tomcat4118\src\webapps\helloblackjack\web\images\a_s.gif
to C:\Tomcat4118\src\webapps\helloblackjack\build\images\a_s.gif
[copy] Copying C:\Tomcat4118\src\webapps\helloblackjack\web\index.html to C
:\Tomcat4118\src\webapps\helloblackjack\build\index.html
[copy] Copying C:\Tomcat4118\src\webapps\helloblackjack\web\newplayer.html
to C:\Tomcat4118\src\webapps\helloblackjack\build\newplayer.html
[copy] Copying C:\Tomcat4118\src\webapps\helloblackjack\web\WEB-INF\web.xml
to C:\Tomcat4118\src\webapps\helloblackjack\build\WEB-INF\web.xml
compile:
[mkdir] Created dir: C:\Tomcat4118\src\webapps\helloblackjack\build\WEB-INF\
classes
[javac] myblackjackpackage\BlackjackDAO.class skipped - don't know how to ha
ndle it
[javac] myblackjackpackage\BlackjackDAO.java added as C:\Tomcat4118\src\weba
pps\helloblackjack\build\WEB-INF\classes\myblackjackpackage\BlackjackDAO.class d
oesn't exist.
[javac] myblackjackpackage\BlackjackServlet.java added as C:\Tomcat4118\src\
webapps\helloblackjack\build\WEB-INF\classes\myblackjackpackage\BlackjackServlet
.class doesn't exist.
[javac] myblackjackpackage\Player.java added as C:\Tomcat4118\src\webapps\he
lloblackjack\build\WEB-INF\classes\myblackjackpackage\Player.class doesn't exist
[javac] Compiling 3 source files to C:\Tomcat4118\src\webapps\helloblackjack
\build\WEB-INF\classes
[javac] Using modern compiler
[javac] Compilation args: -d C:\Tomcat4118\src\webapps\helloblackjack\build\
WEB-INF\classes -classpath
"C:\Tomcat4118\src\webapps\helloblackjack\build\WEB-I
NF\classes;
C:\tomcat4118\common\classes;
C:\tomcat4118\common\lib\activation.jar;
C:\tomcat4118\common\lib\ant.jar;
C:\tomcat4118\common\lib\commons-collections.jar;
C:\tomcat4118\common\lib\commons-dbcp.jar;
C:\tomcat4118\common\lib\commons-logging-api.jar;
C:\tomcat4118\common\lib\commons-pool.jar;
C:\tomcat4118\common\lib\jasper-compiler.jar;
C:\tomcat4118\common\lib\jasper-runtime.jar;
C:\tomcat4118\common\lib\jdbc2_0-stdext.jar;
C:\tomcat4118\common\lib\jndi.jar;
C:\tomcat4118\common\lib\jta.jar;
C:\tomcat4118\common\lib\mail.jar;
C:\tomcat4118\common\lib\mysql_uncomp.jar;
C:\tomcat4118\common\lib\naming-common.jar;
C:\tomcat4118\common\lib\naming-factory.jar;
C:\tomcat4118\common\lib\naming-resources.jar;
C:\tomcat4118\common\lib\servlet.jar;
C:\tomcat4118\common\lib\tools.jar;
C:\j2sdk14003\lib\tools.jar;
C:\tomcat4118\ant141\lib\servlet.jar;
C:\tomcat4118\ant141\lib\jaxp.jar;
C:\tomcat4118\ant141\lib\crimson.jar;
C:\tomcat4118\ant141\lib\ant.jar;
C:\Tomcat4118\src\webapps\helloblackjack;
C:\mysql\jdbc_dvr\mm.mysql.jdbc-1.2c;
C:\Program Files\SQLserverjdbcdriver\lib\msbase.jar;
C:\Program Files\SQLserverjdbcdriver\lib\msutil.jar;
C:\Program Files\SQLserverjdbcdriver\lib\mssqlserver.jar"
-sourcepath C:\Tomcat4118\src\webapps\helloblackjack\src -g -O
[javac] Files to be compiled:
C:\Tomcat4118\src\webapps\helloblackjack\src\myblackjackpackage\BlackjackDAO
.java
C:\Tomcat4118\src\webapps\helloblackjack\src\myblackjackpackage\BlackjackSer
vlet.java
C:\Tomcat4118\src\webapps\helloblackjack\src\myblackjackpackage\Player.java
[javac] C:\Tomcat4118\src\webapps\helloblackjack\src\myblackjackpackage\Blac
kjackServlet.java:55: cannot resolve symbol
[javac] symbol : method addPlayer (javax.servlet.http.HttpServletRequest,j
avax.servlet.http.HttpServletResponse)
[javac] location: class myblackjackpackage.BlackjackServlet
[javac] addPlayer(request, response);
[javac] ^
[javac] 1 error
BUILD FAILED
C:\Tomcat4118\src\webapps\helloblackjack\build.xml:212: Compile failed, messages
should have been provided.
at org.apache.tools.ant.taskdefs.Javac.execute(Javac.java:559)
at org.apache.tools.ant.Task.perform(Task.java:217)
at org.apache.tools.ant.Target.execute(Target.java:184)
at org.apache.tools.ant.Target.performTasks(Target.java:202)
at org.apache.tools.ant.Project.executeTarget(Project.java:601)
at org.apache.tools.ant.Project.executeTargets(Project.java:560)
at org.apache.tools.ant.Main.runBuild(Main.java:454)
at org.apache.tools.ant.Main.start(Main.java:153)
at org.apache.tools.ant.Main.main(Main.java:176)
Total time: 1 second
C:\Tomcat4118\src\webapps\helloblackjack>

yes!
early on i tried: BlackjackDAO.addPlayer(request, response);
instead of: theBlackjackDAO.addPlayer(request, response);
you rock - thanks a ton

Guru question, class reloading, resolved symbols

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