fix: Update 03-jdbc.md (#1101)

* Update 03-jdbc.md

fix demo code

* Update 03-jdbc.md

* Update 03-jdbc.md

* Update 03-jdbc.md

---------

Co-authored-by: Quan <[email protected]>

Author: hantmac

docs/en/developer/00-drivers/03-jdbc.md

@@ -101,7 +101,7 @@ package com.example;
 import java.sql.*;
 import java.util.Properties;
 
-public class demo {
+public class Main {
     // Connecting to a local Databend with a SQL user named 'user1' and password 'abc123' as an example.
     // Feel free to use your own values while maintaining the same format.
     static final String DB_URL = "jdbc:databend://127.0.0.1:8000";
@@ -126,6 +126,8 @@ public class demo {
         stmt.close();
         conn.close();
         System.exit(0);
+    }
+}
 ```
 
 ### Example: Copy into or merge into table
@@ -263,7 +265,7 @@ Before you start, make sure you have successfully created a warehouse and obtain
 <dependency>
     <groupId>com.databend</groupId>
     <artifactId>databend-jdbc</artifactId>
-    <version>0.2.1</version>
+    <version>0.2.8</version>
 </dependency>
 ```
 
@@ -274,11 +276,7 @@ Create a file named `sample.java` with the following code:
 ```java
 package databend_cloud;
 
-import java.sql.SQLException;
-import java.sql.DriverManager;
-import java.sql.Connection;
-import java.sql.Statement;
-import java.sql.ResultSet;
+import java.sql.*;
 import java.util.Properties;
 
 public class sample {
@@ -314,18 +312,18 @@ public class sample {
         ps.setString(5, "[1,2,3,4,5]");
         ps.addBatch();
         int[] ans = ps.executeBatch();
-        Statement statement = c.createStatement();
-
-        System.out.println("execute select on object");
-        statement.execute("SELECT * from objects_test1");
-        ResultSet r = statement.getResultSet();
-
-        while (r.next()) {
-            System.out.println(r.getInt(1));
-            System.out.println(r.getString(2));
-            System.out.println(r.getTimestamp(3).toString());
-            System.out.println(r.getString(4));
-            System.out.println(r.getString(5));
+        Statement s = connection.createStatement();
+
+        System.out.println("execute select on table");
+        statement.execute("SELECT * from sample_test");
+        ResultSet r2 = statement.getResultSet();
+
+        while (r2.next()) {
+            System.out.println(r2.getInt(1));
+            System.out.println(r2.getString(2));
+            System.out.println(r2.getTimestamp(3).toString());
+            System.out.println(r2.getString(4));
+            System.out.println(r2.getString(5));
         }
         connection.close();
     }