Class Definition Error

Question

Hi- when I compile the following code I receive this error message:
Exception in thread "main" java.lang.NoClassDefFoundError: ConnectionPool
Any ideas?
Here's the code:
package databaseConn;
import java.awt.*;
import java.io.*;
import java.util.*;
import java.sql.*;
public class ConnectionPool
     private Hashtable connections=new Hashtable();
     private Properties props;
     public ConnectionPool(Properties props, int initialConnections)
                                   throws SQLException, ClassNotFoundException
          this.props=props;
          initializePool(props,initialConnections);
     public ConnectionPool(String driverClassName, String dbURL, String user,
                                String password, int initialConnections)
                                throws SQLException, ClassNotFoundException
          props=new Properties();
          props.put("connection.driver",driverClassName);
          props.put("connection.url",dbURL);
          props.put("user",user);
          props.put("password",password);
          initializePool(props,initialConnections);
     public Connection getConnection()
          Connection con=null;
          Enumeration cons=connections.keys();
          synchronized(connections)
               while(cons.hasMoreElements())
                    con=(Connection)cons.nextElement();
                    Boolean b= (Boolean) connections.get(con);
                    if(!b.booleanValue())
                         try
                              con.setAutoCommit(true);
                         catch(SQLException e)
                              try
                                   connections.remove(con);
                                   con=getNewConnection();
                              catch(SQLException er)
                         connections.put(con,Boolean.TRUE);
                         return con;
               try
                    con=getNewConnection();
                    connections.put(con,Boolean.FALSE);
               catch(SQLException er)
               return con;     
     public void releaseConnection(Connection released)
          if(connections.containsKey(released))
               connections.put(released,Boolean.FALSE);
     public void initializePool(Properties props, int initialConnections)
                                     throws SQLException, ClassNotFoundException
          Class.forName(props.getProperty("connection.driver"));
          for(int k=0;k<initialConnections;k++)
               Connection con= getNewConnection();
               connections.put(con,Boolean.FALSE);
     public Connection getNewConnection() throws SQLException
          return DriverManager.getConnection(props.getProperty("connection.url"),props);
public class RetrieveInfoFromDB
     ConnectionPool pool;
     ResultSet rs=null;
     Connection con=null;
    public RetrieveInfoFromDB(Connection con)
          this.con=con;
     /*public String[] getInfo(String field,String table)
public class InsertInfoIntoDB
     ConnectionPool pool;
     Connection con;
     public InsertInfoIntoDB(ConnectionPool pool)
          this.pool=pool;
    public InsertInfoIntoDB(Connection con)
          this.con=con;
     public String[][] parseFile(File temp)
          String[][] S=null;
          try
               String file="";
               String line;
               int lines=0;
               int r=0;
               StringTokenizer tok;
               BufferedReader in=new BufferedReader(new FileReader(temp));
               while((line=in.readLine())!=null)
                    file+=line;
                    lines++;
               tok=new StringTokenizer(file,"^'/n'");
               S = new String[lines][2];
               while(tok.hasMoreTokens())
                    line=tok.nextToken();
                    S[r][0]=line;
                    line=tok.nextToken();
                    S[r][1]=line;
                    r++;     
          catch(FileNotFoundException e)
          catch(IOException er)
          return S;
public class WriteToTempFile
     PrintWriter fout;
     public WriteToTempFile(File temp)
          try
               fout=new PrintWriter(new FileWriter(temp));
          catch(IOException e)
     public void writeln(String param1, String param2)
          fout.println(param1+"^"+param2+"^");
     public void flush()
          fout.flush();
     public void close()
          fout.close();
[-code]

Answer 1

If all the code you posted is in one .java file it won't compile because only one class can be declared as public. The file should have he same name as the public class.
Example
MyClass.java
public class MyClass {
  // some code here
class Helper1 {
  // some code for this class
class Helper2 {
  // some more code
The Helper1 and Helper2 classes will only be accessible by MyClass objects. If you want to make them available to other classes as well, define them in different .java files called Helper1.java and Helper2.java.
Hope this helps,
Calin