import java.sql.*; public class mysql {     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 void main(String[] args) throws SQLException {         connect();         operation();         stmt.close();         con.close();     }     public static void test() {         String sql_select = "select * from tablename where id=1";         String sql_insert = "insert into tablename (col1,col2..) values('1','2'...)";         String sql_update = "update tablename set colname='update' where id=1";         //insert(sql_insert);         //select(sql_select);         //update(sql_update);     }     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!");         }     }     public static void select(String sql) {         try {             rs = stmt.executeQuery(sql);             ResultSetMetaData meta_data = rs.getMetaData();//列名             for (int i_col = 1; i_col <= meta_data.getColumnCount(); i_col++) {                 System.out.print(meta_data.getColumnLabel(i_col) + "   ");             }             System.out.println();             while (rs.next()) {                 for (int i_col = 1; i_col <= meta_data.getColumnCount(); i_col++) {                     System.out.print(rs.getString(i_col) + "  ");                 }                 System.out.println();             }             rs.close();         }catch (Exception e) {             System.out.println("数据查询失败!");         }     }     public static void insert(String sql) {         try {             stmt.clearBatch();             stmt.addBatch(sql);             stmt.executeBatch();             System.out.println("数据插入成功!");         }catch (Exception e) {             System.out.println("数据插入失败!");         }     }     public static void update(String sql) {         try {             stmt.executeUpdate(sql);             System.out.println("数据更新成功!");         }catch (Exception e) {             System.out.println("数据更新失败!");         }     } }