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

Question

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

Answer 1

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.