try{  
//加载MySql的驱动类
Class.forName("com.mysql.jdbc.Driver") ;  
}catch(ClassNotFoundException e){  
System.out.println("找不到驱动程序类 ，加载驱动失败！");  
e.printStackTrace() ;  
}  

//连接MySql数据库，用户名和密码都是root
 String url = "jdbc:mysql://localhost:3306/test" ;
 String username = "root" ;  
 String password = "root" ;  
try{  
Connection con =
 DriverManager.getConnection(url , username , password ) ;  
 }catch(SQLException se){  
System.out.println("数据库连接失败！");  
se.printStackTrace() ;  
 }

Statement stmt = con.createStatement() ;  
PreparedStatement pstmt = con.prepareStatement(sql) ;  
CallableStatement cstmt =
con.prepareCall("{CALL demoSp(? , ?)}") ; 

ResultSet rs = stmt.executeQuery("SELECT * FROM ...") ;  
int rows = stmt.executeUpdate("INSERT INTO ...") ;  
boolean flag = stmt.execute(String sql) ;  

package me.clfeng.jdbc;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;

public class DBHelper {

  public static final String url = "jdbc:mysql://localhost:3306/mybatis";
  public static final String name = "com.mysql.jdbc.Driver";
  public static final String username = "root";
  public static final String password = "123456";

  public Connection conn = null;
  public PreparedStatement statement = null;

  public DBHelper(String sql) {
    try {
      Class.forName(name);// 指定连接类型
      conn = DriverManager.getConnection(url, username, password);// 获取连接
      statement = conn.prepareStatement(sql);// 准备执行语句
    } catch (Exception e) {
      e.printStackTrace();
    }
  }
　　//释放资源
  public void close() {
    try {
      this.conn.close();
      this.statement.close();
    } catch (Exception e) {
      e.printStackTrace();
    }

  }
}

package me.clfeng.jdbc;

import java.sql.ResultSet;

public class JdbcTest {
  
  static String sql = null;
  static DBHelper dbHelper = null;
  static ResultSet resultSet = null;

  public static void main(String[] args) {
    sql = "select * from user";
    dbHelper = new DBHelper(sql);

    try {
      resultSet = dbHelper.statement.executeQuery();// 执行语句，得到结果集
      while (resultSet.next()) {
        int id = resultSet.getInt(1);
        String name = resultSet.getString(2);
        int age = resultSet.getInt(3);
        System.out
            .println("id=" + id + ",name=" + name + ",age=" + age);
      }

      resultSet.close();
      dbHelper.close();
    } catch (Exception e) {
      e.printStackTrace();
    }
  }

}