import java.sql.Connection;     import java.sql.DriverManager;     import java.sql.PreparedStatement;     import java.sql.ResultSet;     import java.sql.SQLException;     import java.sql.Statement;      public class classname {      public static String url = "jdbc:mysql://localhost:3306/test";//characterEncoding=GBK      public static String username = "root";      public static String password = "root";      public static Connection con;      public static Statement stmt;      public static ResultSet rs;      public static PreparedStatement pstmt;             public static void main(String[] args) throws SQLException {          connect();          //select();             //insert();             //update();          //delete();             close();      }      public static void connect() {          // 定位驱动          try {              Class.forName("com.mysql.jdbc.Driver");              System.out.println("加载驱动成功!");           } catch (ClassNotFoundException e) {              System.out.println("加载驱动失败!");              e.printStackTrace();          }          // 建立连接          try {              con = DriverManager.getConnection(url, username, password);              stmt = con.createStatement();              System.out.println("数据库连接成功!");           } catch(SQLException e) {              System.out.println("数据库连接失败!");              e.printStackTrace();          }      }      public static void select() {          try {                       String sql="select * from test where name=? ";               pstmt=con.prepareStatement(sql);              pstmt.setString(1,"root");            //String sql="select * from test where name='root' ";               //rs = stmt.executeQuery(sql);             rs=pstmt.executeQuery();              while (rs.next()) {               System.out.println("你的第一个字段内容为："+rs.getString("name"));                System.out.println("你的第二个字段内容为："+rs.getInt(1));               }              rs.close();          }catch (Exception e) {              System.out.println("数据查询失败!");              e.printStackTrace();          }      }      public static void insert() {          try {           String sql="insert into test (id,name) values('2','admin')";           stmt.executeUpdate(sql);              System.out.println("数据插入成功!");          }catch (Exception e) {              System.out.println("数据插入失败!");              e.printStackTrace();          }                 }      public static void update() {          try {           String sql="update test set name='rootroot' where id=1";              stmt.executeUpdate(sql);              System.out.println("数据更新成功!");          }catch (Exception e) {              System.out.println("数据更新失败!");              e.printStackTrace();          }      }      public static void delete() {          try {           String sql="delete from test where id=?";            pstmt = con.prepareStatement(sql);               pstmt.setInt(1,1);               pstmt.executeUpdate();              System.out.println("数据删除成功!");          }catch (Exception e) {              System.out.println("数据删除失败!");              e.printStackTrace();          }      }      public static void close() {       try{        if(rs!=null)               rs.close();        if(stmt!=null)               stmt.close();        if(con!=null)               con.close();       }catch(Exception e)       {        e.printStackTrace();       }      }         }