JDBC性能优化续

代码细节优化：

package cn.itcast.jdbc.datasource;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.util.LinkedList;
import java.util.List;

public class MyDataSource {

    private static String url="jdbc:mysql://localhost:3306/jdbc";
    private static String user="root";
    private static String password="admin";
    private static int initCount=5;
    private static int maxCount=10;
    private int currentCount=0;
    private LinkedList<Connection> connectionsPool=new LinkedList<Connection>();

    public MyDataSource(){
        for(int i=0;i<initCount;i++){
             try {
                 //先入先出的算法
                this.connectionsPool.addLast(this.createConnection());
                this.currentCount++;
            } catch (SQLException e) {
                throw new ExceptionInInitializerError(e);
            }
        }
    }

     public Connection getConnection() throws SQLException{
         synchronized(connectionsPool){
             if(connectionsPool.size()>0)
             return this.connectionsPool.removeFirst();
             if(this.currentCount<maxCount){
                 this.currentCount++;
                 return this.createConnection();
             }
            throw new SQLException("已没有连接！");
         }
     }
     private Connection createConnection() throws SQLException{
         return DriverManager.getConnection(url, user, password);
     }

     public void free(Connection conn){
         this.connectionsPool.addLast(conn);
     }
}

多线程并发问题、并发获取连接可能会出现安全问题，需要给代码加上同步块，使其串行获取连接，即加上锁。