ConnectionPool2.class

//Creates a pool of database connections.
package com;
import java.sql.*;
import java.util.*;

public class ConnectionPool2
{
static Stack st = new Stack();
static Connection connect;
static Connection connection3;
static int flag = 0;
static int count = 20;

public static void ConnectionPool2()
    {
    }
public static void start()
    {
    System.out.println("connection pool started");
    if( flag == 1)
    count = 5;

while(st.size()<count)
        {
        String url = "jdbc:odbc:PayRollDatabase";
        String username = "house";
        String password = "flower";
        try
            {
            Class.forName( "sun.jdbc.odbc.JdbcOdbcDriver" );
            connection3 = DriverManager.getConnection(
                              url, username, password );

}
        catch (ClassNotFoundException cnf)
            {
            }
        catch (SQLException sqlex)
            {
            }
            System.out.println("new connection instantiated");
        st.push(connection3);
        }
    flag = 1; //First time round the flag = 0 and so a full 20 connections are created in
//subsequent rounds only 5 are created for top up.
    }
public static Connection getConnection()
    {
//If the stack is not empty
    if (!st.empty())
        {
//If the number of connections open are greater than twenty close some
        if(st.size()>20)
            {
            closeConnections();
            }
        connect = (Connection)st.pop();
        }
    else
        {
        start();
        connect = (Connection)st.pop();
//Another Method is needed here to create more connections when the stack is empty
        }
    return connect;
    }
//After use the connection is returned to the stack for reuse
public static void returnConnection(Connection c)
    {
    st.push(c);
    }
//Method called above when the number of connections becomes to great.
public static void closeConnections()
    {
    for(int i = 0; i <= 8;i++)
        {
        try
            {
            Connection con = (Connection)st.pop();
            con.close();
            }
            catch(SQLException sq)
            {
            }
        }
    }
}