Cassandra difference between com.datastax.oss -> java-driver-core and com.datastax.cassandra -> cassandra-driver-core

I wrote a program with the following package

<dependency>
   <groupId>com.datastax.cassandra</groupId>
   <artifactId>cassandra-driver-core</artifactId>
   <version>3.6.0</version>
</dependency>

But when I change it to 4.0.0 it doesn't have some critical classes.

I search and read in Datastax that I must use the following package:

<dependency>
  <groupId>com.datastax.oss</groupId>
  <artifactId>java-driver-core</artifactId>
  <version>4.0.0</version>
</dependency>

So, it totally have different classes, So what is the right package from Datastax to use in java for connecting and working with Cassandra? Which one is better to use and what is the main difference?

Solution

This really depends on your requirements:

if you're developing completely new application, then you need to use 4.x versions of the driver, as 3.x won't get new functionality, only critical bug fixes. Latest version right now is 4.9.0 - check documentation for exact Maven definition - it should match your second snippet. Please take into account that this driver is quite different from the 3.x versions, so copy-pasting old examples won't work, but you can follow the upgrade guide to translate them to the new version.
if you have existing code, then you may stick to the latest 3.x version (3.10 right now) because porting to 4.x versions could lead to significant rewrite of application caused by architectural changes in new version. Consult upgrade guide for details of porting. Also, you can check following repository for examples of code ported to 4.x.