How can we write connection pooling using Vector, ArrayList classes in java??

//Comment
package connection.pooling;

import java.sql.Connection;
import java.sql.DriverManager;
import java.util.Vector;

public class ConnectionPooling {

Vector connections = null;
static ConnectionPooling instance = null;
public static final int MAX_CONNECTIONS = 10;

private ConnectionPooling() {
initialize();
}

public synchronized void removeAllConnections() {

if (connections == null) {
return;
}

try {
int sz = connections.size();
for (int i = 0; i < sz / 2; i++) {   
 connections.remove(i);   
 System.out.println("Removing Connection " + i);  
}
if (connections != null && connections.size() > 0) {
 connections.removeAllElements();
 System.out.println("Removing all the remaining Connections");
}
connections = null;
} catch (Exception e) {
System.out.println("Error " + e);
}
instance = null;

}

public static synchronized ConnectionPooling getInstance() {
if (instance == null)
instance = new ConnectionPooling();

return instance;
}

public synchronized void initialize() {

if (connections == null) {

try {
 Class.forName("com.mysql.jdbc.Driver");
 connections = new Vector();
 int count = 0;
 while (count < MAX_CONNECTIONS) {    
    Connection c = DriverManager.getConnection("jdbc:mysql://localhost/test",
                                          "root", "root");    
    connections.addElement(c);  
    count++;
 }
 System.out.println("total connections created r: " + count);
} catch (Exception e) {
  System.out.println("initialise:Exception");
  e.printStackTrace();
  instance.removeAllConnections();
}
}
}
public synchronized Connection getConnection() {
  System.out.println("getConnection");
  Connection c = null; 
  if (connections == null)
      return null;
  if (connections.size() > 0) {
    c = (Connection) connections.elementAt(0);
    connections.removeElementAt(0);
  }
return c;
}

public synchronized void putConnection(Connection c) {

if (c != null) {
connections.addElement(c);
notifyAll();
}
}

public static void main(String[] args) {
ConnectionPooling cp = ConnectionPooling.getInstance();
cp.removeAllConnections();
}
}