编写一个基本的连接池来实现连接的复用&一些工程细节上的优化

package it.cast.jdbc;

import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

public class Base {

static Connection conn = null;

public static void main(String[] args) throws SQLException, ClassNotFoundException {
for (int i = 0; i < 20; i++) {
Connection conn = jdbcUtils.getConnection();
System.out.println(conn);
//jdbcUtils.free(null, null, conn);
}
}

static void test() throws SQLException, ClassNotFoundException {

// 2.建立连接
conn = jdbcUtils.getConnection();

// 3.创建语句
Statement st = conn.createStatement();

// 4.执行语句
ResultSet rs = st.executeQuery("select * from user");

// 5.处理结果
while (rs.next()) {
System.out.println(rs.getObject(1) + "\t" + rs.getObject(2) + "\t"
+ rs.getObject(3)+"\t" + rs.getObject(4));
}

//6.释放资源
jdbcUtils.free(rs, st, conn);
}

}