JAVA接続プール技術(javaデータベースプログラミング)

                     ，           ，           ，           。                

import java.io.FileNotFoundException;
import java.io.IOException;
import java.sql.Connection;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;
import java.util.Properties;
import java.sql.*;


public class ConnectionPool {
	private List<Connection> pooList=null;//       
	Properties props=null;
	String userName=null;
	String password=null;
	String url=null;
	String driverName=null;
	int maxSize=0;
	Connection connection=null;
	private static ConnectionPool pool=null;//     
	private  ConnectionPool(int max)throws ClassNotFoundException,FileNotFoundException,IOException
	{
		userName="root";
		password="123456";
		url="jdbc:mysql://localhost/student";
		driverName="com.mysql.jdbc.Driver";
		maxSize=max;
		Class.forName(driverName);
		pooList=new ArrayList<Connection>();
		
		
	}
	//     
	public synchronized Connection getConnection()throws SQLException
	{
		
		if(pooList.size()==0)
		{
			for (int i = 0; i < maxSize; i++) 
			{
				connection=driverName.getConnection(url,userName,password);
				pooList.add(connection);
			}
		}
		return pooList.remove(0);
		
	}
	//     
	public void close(Connection connection)throws SQLException
	{
		System.out.println(pooList.size());
		if(pooList.size()<maxSize)
		{
			pooList.add(connection);
			
		}
		else
		{
			connection.close();
		}
		System.out.println(pooList.size());
	}
	//         
	public static ConnectionPool getinstance()throws FileNotFoundException,ClassNotFoundException,IOException
	{
		if(pool==null)
		{
			pool=new ConnectionPool(10);
		}
		return pool;
	}
	
	

}