// 加载MySQL驱动程序
Class.forName("com.mysql.cj.jdbc.Driver");// 建立连接
String url = "jdbc:mysql://localhost/database_name";
String username = "username";
String password = "password";
Connection conn = DriverManager.getConnection(url, username, password);

Statement stmt = conn.createStatement();
ResultSet rs = stmt.executeQuery("SELECT * FROM table_name");

 String query = "SELECT * FROM table_name WHERE column = ?";PreparedStatement pstmt = conn.prepareStatement(query);pstmt.setString(1, "value");ResultSet rs = pstmt.execute Query();