import java.sql.Connection;        import java.sql.DriverManager;        import java.sql.ResultSet;        import java.sql.SQLException;        import java.sql.Statement;                public class DBUtil {            public static final String DRIVER = "com.mysql.jdbc.Driver";            public static final String URL = "jdbc:mysql://localhost:3306/db";            public static final String USERNAME = "root";            public static final String PASSWORD = "root";                    /**            * 通过静态代码块 注册数据库驱动            */            static {                try {                    Class.forName(DRIVER);                } catch (ClassNotFoundException e) {                    e.printStackTrace();                }            }                    /**            * 获得Connection            *             * @return            */            public static Connection getConnection() {                Connection conn = null;                try {                    conn = DriverManager.getConnection(URL, USERNAME, PASSWORD);                } catch (SQLException e) {                    e.printStackTrace();                }                return conn;            }                    /**            * 获得Statement            *             * @return            */            public static Statement getStatement() {                Statement st = null;                try {                    st = getConnection().createStatement();                } catch (SQLException e) {                    e.printStackTrace();                }                return st;            }                    /**            * 关闭ResultSet            *             * @param rs            */            public static void closeResultSet(ResultSet rs) {                if (rs != null) {                    try {                        rs.close();                    } catch (SQLException e) {                        e.printStackTrace();                    }                }            }                    /**            * 关闭Statement            *             * @param st            */            public static void closeStatement(Statement st) {                if (st != null) {                    try {                        st.close();                    } catch (SQLException e) {                        e.printStackTrace();                    }                }            }                    /**            * 关闭Connection            *             * @param conn            */            public static void closeConnection(Connection conn) {                if (conn != null) {                    try {                        conn.close();                    } catch (SQLException e) {                        e.printStackTrace();                    }                }            }                    /**            * 关闭全部            *             * @param rs            * @param sta            * @param conn            */            public static void closeAll(ResultSet rs, Statement sta, Connection conn) {                closeResultSet(rs);                closeStatement(sta);                closeConnection(conn);            }                }